Don't build code with _GNU_SOURCE, use _XOPEN_SOURCE=500 instead.

_GNU_SOURCE is only now for xbps_xasprintf() if vasprintf is found,
and only for <stdio.h>, it's unset immediately once the header is included.

bin/xbps-repo/main.c

@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2008-2010 Juan Romero Pardines.
+ * Copyright (c) 2008-2011 Juan Romero Pardines.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -27,6 +27,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <errno.h>
 #include <limits.h>
 #include <libgen.h>