tools: Use $(top_builddir) instead of relative path to fix out of tree build
diff --git a/tools/Makefile.am b/tools/Makefile.am
index 7449401..df6c803 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -6,5 +6,5 @@
 iproxy_SOURCES = iproxy.c
 iproxy_CFLAGS = $(AM_CFLAGS)
 iproxy_LDFLAGS = $(AM_LDFLAGS)
-iproxy_LDADD = ../src/libusbmuxd.la
+iproxy_LDADD = $(top_builddir)/src/libusbmuxd.la