zlib detection fix by (Gildas Bazin <gbazin altern org<)

Originally committed as revision 4048 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -854,7 +854,7 @@ if (zlibVersion() != ZLIB_VERSION)
 return 0;
 }
 EOF
-$cc $CFLAGS -o $TMPE $TMPC -lz 2> /dev/null || zlib="no"
+$cc $CFLAGS $LDFLAGS -o $TMPE $TMPC -lz 2> /dev/null || zlib="no"
 # $TMPE 2> /dev/null > /dev/null || zlib="no"
 # XXX: more tests needed - runtime test
 fi