Do not clean zip_err_str.c since this breaks the cmake build.

--HG--
branch : HEAD

lib/Makefile.am

diff --git a/lib/Makefile.am b/lib/Makefile.am
index 31bd17a..f088569 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -84,7 +84,7 @@
 	zip_unchange_data.c \
 	zip_utf-8.c
 
-BUILT_SOURCES=zip_err_str.c zipconf.h
+BUILT_SOURCES=zipconf.h
 CLEANFILES=	${BUILT_SOURCES}
 
 EXTRA_DIST=	CMakeLists.txt \