ART: Enable more Clang warnings

Change-Id: Ie6aba02f4223b1de02530e1515c63505f37e184c
diff --git a/build/Android.common_build.mk b/build/Android.common_build.mk
index 8b4be82..8eeeec6 100644
--- a/build/Android.common_build.mk
+++ b/build/Android.common_build.mk
@@ -141,6 +141,9 @@
 # Enable warning for deprecated language features.
 art_clang_cflags += -Wdeprecated
 
+# Enable warning for unreachable break & return, and missing NO_RETURN annotations.
+art_clang_cflags += -Wunreachable-code-break -Wunreachable-code-return -Wmissing-noreturn
+
 
 # GCC-only warnings.
 art_gcc_cflags := -Wunused-but-set-parameter