_FORTIFY_SOURCE: check for integer overflows

Ensure that strcat / strncat check for integer overflows
when computing the length of the resulting string.

Change-Id: Ib806ad33a0d3b50876f384bc17787a28f0dddc37
diff --git a/libc/Android.mk b/libc/Android.mk
index 70a5243..f2784fd 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -537,7 +537,8 @@
 libc_common_c_includes := \
 		$(LOCAL_PATH)/stdlib  \
 		$(LOCAL_PATH)/string  \
-		$(LOCAL_PATH)/stdio
+		$(LOCAL_PATH)/stdio   \
+		external/safe-iop/include
 
 # Needed to access private/__dso_handle.h from
 # crtbegin_xxx.S and crtend_xxx.S