uclibc only defines strndup(3) if _GNU_SOURCE is defined

References #516.

src/libcharon/config/ike_cfg.c

@@ -14,12 +14,12 @@
  * for more details.
  */
 
-#include "ike_cfg.h"
-
+#define _GNU_SOURCE /* for stdndup() */
 #include <string.h>
 
-#include <daemon.h>
+#include "ike_cfg.h"
 
+#include <daemon.h>
 
 ENUM(ike_version_names, IKE_ANY, IKEV2,
 	"IKEv1/2",

src/libcharon/sa/xauth/xauth_manager.c

@@ -13,6 +13,9 @@
  * for more details.
  */
 
+#define _GNU_SOURCE /* for stdndup() */
+#include <string.h>
+
 #include "xauth_manager.h"
 
 #include <collections/linked_list.h>