Add arping to debug builds. am: d888244c9d
am: 019d96d2b8

Change-Id: Id4c5959fd56ccfa1922807dd2e05a52df7e4f475
diff --git a/Android.mk b/Android.mk
index 5e32066..4bc8f44 100644
--- a/Android.mk
+++ b/Android.mk
@@ -1,6 +1,7 @@
 LOCAL_PATH:= $(call my-dir)
 
 iputils_cflags := \
+  -D_GNU_SOURCE \
   -Wno-missing-field-initializers \
   -Wno-sign-compare \
   -Wno-unused-parameter \