Only define a local environ when not using the prototype from unistd.h
diff --git a/networking/ifupdown.c b/networking/ifupdown.c
index 1842be5..f93f502 100644
--- a/networking/ifupdown.c
+++ b/networking/ifupdown.c
@@ -150,7 +150,9 @@
 
 static char no_act = 0;
 static char verbose = 0;
+#ifndef __USE_GNU
 static char **environ = NULL;
+#endif
 
 #ifdef CONFIG_FEATURE_IFUPDOWN_IP