Force some clang Werrors that *will* break things.

Clang is really aggressive at optimizing a handful of cases (read:
clang will ruin your day some if you write bad code). Fortunately, it
also emits a warning when it's about to do this.

To prevent anyone from suffering from these optimizations, make these
warnings errors and make them impossible to disable.

Change-Id: I5e10bb0fc2ca23190017da716b3b84635577a0bd
diff --git a/core/product.mk b/core/product.mk
index 46fad89..ac5f854 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -270,6 +270,7 @@
 _product_stash_var_list += \
 	GLOBAL_CFLAGS_NO_OVERRIDE \
 	GLOBAL_CPPFLAGS_NO_OVERRIDE \
+	GLOBAL_CLANG_CFLAGS_NO_OVERRIDE \
 
 #
 # Stash values of the variables in _product_stash_var_list.