g++ fix warning on define

JacobBarthelmeh · JacobBarthelmeh · commit 3f52af5e45df · 2022-08-22T17:34:49.000-06:00
diff --git a/apps/wolfsshd/auth.c b/apps/wolfsshd/auth.c
@@ -26,7 +26,9 @@
 
 #ifdef __linux__
     #define _XOPEN_SOURCE
-    #define _GNU_SOURCE
+    #ifndef _GNU_SOURCE
+        #define _GNU_SOURCE
+    #endif
 #endif
 #include <unistd.h>
 
