Add -std=gnu++11 to test cflags

Change-Id: Ife92cea10021658eba6e22a7ebc9e31f3d194a25
diff --git a/liblog/tests/Android.mk b/liblog/tests/Android.mk
index 6c72138..615a657 100644
--- a/liblog/tests/Android.mk
+++ b/liblog/tests/Android.mk
@@ -59,7 +59,8 @@
     -g \
     -Wall -Wextra \
     -Werror \
-    -fno-builtin
+    -fno-builtin \
+    -std=gnu++11
 
 test_src_files := \
     liblog_test.cpp