preserve passed in CFLAGS
diff --git a/configure.in b/configure.in
index c74ab25..d8da057 100644
--- a/configure.in
+++ b/configure.in
@@ -135,6 +135,7 @@
 AC_SUBST(FLaC__SIZE64)
 AC_SUBST(FLaC__USIZE64)
 
+SAVE_CFLAGS="$CFLAGS"
 CFLAGS='-I./include -I $(top_srcdir)/include -Wall -W'
 if test x$debug = xtrue; then
 CFLAGS="$CFLAGS -g -O0 -DDEBUG"
@@ -144,6 +145,7 @@
 		CFLAGS="$CFLAGS -fomit-frame-pointer -funroll-loops -finline-functions -Winline -DFLAC__INLINE=__inline__"
 	fi
 fi
+CFLAGS="$CFLAGS $SAVE_CFLAGS"
 
 AC_OUTPUT(	Makefile	\
 	src/Makefile	\