[libpng16] Allow an easy replacement of the default pre-built configuration

header with a custom header, via the make PNGLIBCONF_H_PREBUILT
macro.
diff --git a/scripts/makefile.amiga b/scripts/makefile.amiga
index 228b5c2..02671a9 100644
--- a/scripts/makefile.amiga
+++ b/scripts/makefile.amiga
@@ -31,6 +31,10 @@
 # make directory command
 MKDIR= makedir
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -43,8 +47,8 @@
 
 $(OBJS): pngpriv.h png.h pngconf.h pnglibconf.h pnginfo.h pngstruct.h pngdebug.h
 
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
-$(CP) scripts/pnglibconf.h.prebuilt pnglibconf.h
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
+	$(CP) $< $@
 
 pngtest: pngtest.o libpng.lib
 $(LN) <WITH <
diff --git a/scripts/makefile.atari b/scripts/makefile.atari
index 3c54b84..d0aa481 100644
--- a/scripts/makefile.atari
+++ b/scripts/makefile.atari
@@ -29,6 +29,10 @@
 # you execute make install.
 DESTDIR=
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = $(LBR)(png.o) $(LBR)(pngset.o) $(LBR)(pngget.o) $(LBR)(pngrutil.o)\
 	$(LBR)(pngtrans.o) $(LBR)(pngwutil.o)\
 	$(LBR)(pngread.o) $(LBR)(pngerror.o) $(LBR)(pngwrite.o)\
@@ -44,7 +48,7 @@
 
 $(OBJS): pngpriv.h png.h pngconf.h pnglibconf.h pnginfo.h pngstruct.h pngdebug.h
 
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	cp $< $@
 
 pngtest.ttp: pngtest.o $(LBR)
diff --git a/scripts/makefile.bc32 b/scripts/makefile.bc32
index 26b8b1f..6fece9c 100644
--- a/scripts/makefile.bc32
+++ b/scripts/makefile.bc32
@@ -50,6 +50,10 @@
 # -M  generate map file
 LDFLAGS=-L$(ZLIB_DIR) -M $(LDEBUG)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 ## Variables
 OBJS = \
 	png.obj \
@@ -112,9 +116,7 @@
 
 ## Minor Targets
 
-# see scripts\pnglibconf.mak for how to make this file
-# with different options
-pnglibconf.h: scripts\pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 png.obj: png.c png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
diff --git a/scripts/makefile.beos b/scripts/makefile.beos
index da62e98..edac365 100644
--- a/scripts/makefile.beos
+++ b/scripts/makefile.beos
@@ -69,6 +69,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -82,8 +86,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# try include scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.bor b/scripts/makefile.bor
index 70236d6..254de89 100644
--- a/scripts/makefile.bor
+++ b/scripts/makefile.bor
@@ -58,6 +58,10 @@
 # -M  generate map file
 LDFLAGS=-M -L$(ZLIB_DIR) $(MODEL_ARG) $(LDEBUG)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 ## Variables
 
 OBJS = \
@@ -111,8 +115,8 @@
 
 all: libpng pngtest
 
-# try !inlude scripts\pnglibconf.mak for more options
-pnglibconf.h: scripts\pnglibconf.h.prebuilt
+# try !include scripts\pnglibconf.mak for more options
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng: $(LIBNAME)
diff --git a/scripts/makefile.darwin b/scripts/makefile.darwin
index e463099..fd6adff 100644
--- a/scripts/makefile.darwin
+++ b/scripts/makefile.darwin
@@ -63,6 +63,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -79,8 +83,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.dec b/scripts/makefile.dec
index 3096c1e..54cbcac 100644
--- a/scripts/makefile.dec
+++ b/scripts/makefile.dec
@@ -58,6 +58,10 @@
 CFLAGS=-std -w1 -O # -g
 LDFLAGS=-L$(ZLIBLIB) -rpath $(ZLIBLIB) libpng.a -lz -lm
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -67,8 +71,7 @@
 
 all: $(LIBSO) libpng.a pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.dj2 b/scripts/makefile.dj2
index 0ff3913..e21546d 100644
--- a/scripts/makefile.dj2
+++ b/scripts/makefile.dj2
@@ -22,6 +22,10 @@
 CP=cp
 RM_F=rm -f
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o pngwtran.o \
 	pngmem.o pngerror.o pngpread.o
@@ -31,8 +35,7 @@
 
 all: libpng.a pngtest
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.elf b/scripts/makefile.elf
index cdfbca9..e595d95 100644
--- a/scripts/makefile.elf
+++ b/scripts/makefile.elf
@@ -83,6 +83,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -99,8 +103,7 @@
 
 all: libpng.a $(LIBSO) pngtest pngtest-static libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.freebsd b/scripts/makefile.freebsd
index 3add34a..c008435 100644
--- a/scripts/makefile.freebsd
+++ b/scripts/makefile.freebsd
@@ -39,6 +39,10 @@
 CPPFLAGS+=	-I. -I${ZLIBINC}
 CFLAGS+=	-W -Wall
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT= scripts/pnglibconf.h.prebuilt
+
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
@@ -55,8 +59,7 @@
 test: pngtest
 	./pngtest
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	cp $< $@
 
 DOCS = ANNOUNCE CHANGES INSTALL KNOWNBUG LICENSE README TODO Y2KINFO
diff --git a/scripts/makefile.gcc b/scripts/makefile.gcc
index 3e1b84f..8811a28 100644
--- a/scripts/makefile.gcc
+++ b/scripts/makefile.gcc
@@ -30,6 +30,10 @@
 # File extensions
 EXEEXT =
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 # Variables
 OBJS =  png.o pngerror.o pngget.o pngmem.o pngpread.o \
 	pngread.o pngrio.o pngrtran.o pngrutil.o pngset.o \
@@ -38,8 +42,7 @@
 # Targets
 all: static
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 .c.o:
diff --git a/scripts/makefile.hp64 b/scripts/makefile.hp64
index 388babf..2883d65 100644
--- a/scripts/makefile.hp64
+++ b/scripts/makefile.hp64
@@ -68,6 +68,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -84,8 +88,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.hpux b/scripts/makefile.hpux
index 429d8e9..2a4a0b3 100644
--- a/scripts/makefile.hpux
+++ b/scripts/makefile.hpux
@@ -66,6 +66,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -82,8 +86,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.ibmc b/scripts/makefile.ibmc
index 1571d0e..2f5a03c 100644
--- a/scripts/makefile.ibmc
+++ b/scripts/makefile.ibmc
@@ -28,6 +28,10 @@
 CFLAGS = -Mc -O2 -W3
 LDFLAGS =
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 # File extensions
 O=.obj
 A=.lib
@@ -46,8 +50,7 @@
 
 all: libpng$(A) pngtest$(E)
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng$(A): $(OBJS)
diff --git a/scripts/makefile.intel b/scripts/makefile.intel
index cdc7526..9fa963f 100644
--- a/scripts/makefile.intel
+++ b/scripts/makefile.intel
@@ -38,6 +38,10 @@
 LDFLAGS=/SUBSYSTEM:CONSOLE /NOLOGO
 CP=cp
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 O=.obj
 
 OBJS=png$(O) pngset$(O) pngget$(O) pngrutil$(O) pngtrans$(O) pngwutil$(O) \
@@ -46,8 +50,7 @@
 
 all: test
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 png$(O): png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
diff --git a/scripts/makefile.knr b/scripts/makefile.knr
index 7395f65..38a67cb 100644
--- a/scripts/makefile.knr
+++ b/scripts/makefile.knr
@@ -39,14 +39,17 @@
 CP = cp
 RM_F = rm -f
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
 
 all: ansi2knr libpng.a pngtest
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 # general rule to allow ansi2knr to work
diff --git a/scripts/makefile.linux b/scripts/makefile.linux
index 6d62dcd..9fb3cec 100644
--- a/scripts/makefile.linux
+++ b/scripts/makefile.linux
@@ -76,6 +76,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS =  png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -92,8 +96,7 @@
 
 all: libpng.a $(LIBSO) pngtest pngtest-static libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.mips b/scripts/makefile.mips
index 2297126..d171dc4 100644
--- a/scripts/makefile.mips
+++ b/scripts/makefile.mips
@@ -32,6 +32,10 @@
 
 CP=cp
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -41,8 +45,7 @@
 
 all: libpng.a pngtest
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.msc b/scripts/makefile.msc
index f2f1d28..6e30e81 100644
--- a/scripts/makefile.msc
+++ b/scripts/makefile.msc
@@ -19,6 +19,10 @@
 CP=copy
 O=.obj
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 #uncomment next to put error messages in a file
 ERRFILE= >> pngerrs
 
@@ -29,8 +33,7 @@
 
 all: libpng.lib
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 png$(O): png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
diff --git a/scripts/makefile.msys b/scripts/makefile.msys
index 151597c..28af2b9 100644
--- a/scripts/makefile.msys
+++ b/scripts/makefile.msys
@@ -74,6 +74,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 # Variables
 OBJS =  png.o pngerror.o pngget.o pngmem.o pngpread.o \
 	pngread.o pngrio.o pngrtran.o pngrutil.o pngset.o \
@@ -82,8 +86,7 @@
 # Targets
 all: static shared
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 .c.o:
diff --git a/scripts/makefile.ne12bsd b/scripts/makefile.ne12bsd
index 85ae6e8..48c3452 100644
--- a/scripts/makefile.ne12bsd
+++ b/scripts/makefile.ne12bsd
@@ -37,8 +37,7 @@
 .c.o:
 	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	cp $< $@
 
 pngtest.o:	pngtest.c
diff --git a/scripts/makefile.netbsd b/scripts/makefile.netbsd
index a6831e1..776f0c1 100644
--- a/scripts/makefile.netbsd
+++ b/scripts/makefile.netbsd
@@ -26,6 +26,10 @@
 
 CPPFLAGS+=-I${.CURDIR}
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT= scripts/pnglibconf.h.prebuilt
+
 # We should be able to do something like this instead of the manual
 # uncommenting, but it core dumps for me at the moment:
 # .if ${MACHINE_ARCH} == "i386"
@@ -37,8 +41,7 @@
 .c.o:
 	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	cp $< $@
 
 pngtest.o:	pngtest.c
diff --git a/scripts/makefile.openbsd b/scripts/makefile.openbsd
index 5599d75..a1dccc8 100644
--- a/scripts/makefile.openbsd
+++ b/scripts/makefile.openbsd
@@ -31,11 +31,14 @@
 DOCS=	ANNOUNCE CHANGES INSTALL KNOWNBUG LICENSE README TODO Y2KINFO \
 	libpng-manual.txt
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT= scripts/pnglibconf.h.prebuilt
+
 .c.o:
 	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	cp $< $@
 
 pngtest.o:	pngtest.c
diff --git a/scripts/makefile.sco b/scripts/makefile.sco
index 8fd66c7..6e5457d 100644
--- a/scripts/makefile.sco
+++ b/scripts/makefile.sco
@@ -62,6 +62,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -78,8 +82,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.sggcc b/scripts/makefile.sggcc
index 5bcc0e5..f8721c9 100644
--- a/scripts/makefile.sggcc
+++ b/scripts/makefile.sggcc
@@ -72,6 +72,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS =  png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -81,8 +85,7 @@
 
 all: libpng.a pngtest shared libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.sgi b/scripts/makefile.sgi
index 381ac55..561ce83 100644
--- a/scripts/makefile.sgi
+++ b/scripts/makefile.sgi
@@ -75,6 +75,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS =  png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -84,8 +88,7 @@
 
 all: libpng.a pngtest shared libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.so9 b/scripts/makefile.so9
index 220d864..9102e69 100644
--- a/scripts/makefile.so9
+++ b/scripts/makefile.so9
@@ -72,6 +72,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -88,8 +92,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.solaris b/scripts/makefile.solaris
index 92a5bed..879e6a4 100644
--- a/scripts/makefile.solaris
+++ b/scripts/makefile.solaris
@@ -68,6 +68,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -84,8 +88,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.solaris-x86 b/scripts/makefile.solaris-x86
index 630ba1e..509d5a3 100644
--- a/scripts/makefile.solaris-x86
+++ b/scripts/makefile.solaris-x86
@@ -67,6 +67,10 @@
 DL=$(DESTDIR)$(LIBPATH)
 DM=$(DESTDIR)$(MANPATH)
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -83,8 +87,7 @@
 
 all: libpng.a $(LIBSO) pngtest libpng.pc libpng-config
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.std b/scripts/makefile.std
index db731c9..75bb2de 100644
--- a/scripts/makefile.std
+++ b/scripts/makefile.std
@@ -45,6 +45,10 @@
 CFLAGS = -O # -g
 LDFLAGS = -L. -L$(ZLIBLIB) -lpng -lz -lm
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
diff --git a/scripts/makefile.sunos b/scripts/makefile.sunos
index ce2a7f2..df661bf 100644
--- a/scripts/makefile.sunos
+++ b/scripts/makefile.sunos
@@ -44,6 +44,10 @@
 CFLAGS=-O # $(WARNMORE)
 LDFLAGS=-L. -L$(ZLIBLIB) -lpng -lz -lm
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 OBJS = png.o pngset.o pngget.o pngrutil.o pngtrans.o pngwutil.o \
 	pngread.o pngrio.o pngwio.o pngwrite.o pngrtran.o \
 	pngwtran.o pngmem.o pngerror.o pngpread.o
@@ -53,8 +57,7 @@
 
 all: libpng.a pngtest
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 libpng.a: $(OBJS)
diff --git a/scripts/makefile.tc3 b/scripts/makefile.tc3
index 43f8a84..e4744a7 100644
--- a/scripts/makefile.tc3
+++ b/scripts/makefile.tc3
@@ -14,6 +14,10 @@
 LDFLAGS=-m$(MODEL) -L..\zlib
 CP=copy
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 O=.obj
 E=.exe
 
@@ -27,8 +31,7 @@
 
 all: libpng$(MODEL).lib pngtest$(E)
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts/pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $< $@
 
 pngtest: pngtest$(E)
diff --git a/scripts/makefile.vcwin32 b/scripts/makefile.vcwin32
index 4b9c7d7..b17f6a4 100644
--- a/scripts/makefile.vcwin32
+++ b/scripts/makefile.vcwin32
@@ -22,6 +22,10 @@
 CP = copy
 RM = del
 
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
 # File extensions
 O=.obj
 
@@ -37,8 +41,7 @@
 # Targets
 all: libpng.lib
 
-# see scripts/pnglibconf.mak for more options
-pnglibconf.h: scripts\pnglibconf.h.prebuilt
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
        $(CP) $< $@
 
 png$(O): png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h