Android.mk: replace std=c99 with std=gnu99

The android makefiles were passing the -std=c99 flag to the
compiler which disables the typeof keyword. This causes a
build fail for a recent addition to igt_aux.h.
Change this to -std=gnu99, which is the flag used in the
linux build

Signed-off-by: Tim Gore <tim.gore@intel.com>
Signed-off-by: Thomas Wood <thomas.wood@intel.com>
diff --git a/benchmarks/Android.mk b/benchmarks/Android.mk
index 5bb8ef5..14fc0a7 100644
--- a/benchmarks/Android.mk
+++ b/benchmarks/Android.mk
@@ -11,7 +11,7 @@
 
     LOCAL_CFLAGS += -DHAVE_STRUCT_SYSINFO_TOTALRAM
     LOCAL_CFLAGS += -DANDROID -UNDEBUG -include "check-ndebug.h"
-    LOCAL_CFLAGS += -std=c99
+    LOCAL_CFLAGS += -std=gnu99
     # FIXME: drop once Bionic correctly annotates "noreturn" on pthread_exit
     LOCAL_CFLAGS += -Wno-error=return-type
     # Excessive complaining for established cases. Rely on the Linux version warnings.