Add a macro GCC_VERSION and use it to control code paths.

Code paths that work on lower version of GCC are required because
Mac OS will never move beyond GCC 4.2. I added the code paths so
that Mac builds can pass.

Change-Id: I4a3340355133dff4a5107b94970bc809d9de264e
diff --git a/build/Android.common.mk b/build/Android.common.mk
index c6e7366..9e05a1c 100644
--- a/build/Android.common.mk
+++ b/build/Android.common.mk
@@ -45,7 +45,7 @@
 	-fstrict-aliasing
 
 ifeq ($(HOST_OS),linux)
-art_non_debug_cflags := \
+  art_non_debug_cflags := \
 	-Wframe-larger-than=1728
 endif