libcpustats: Turn on -Werror

- Switch to static_assert from deprecated utils/Debug.h
- Turn on C++11 standard
- Turn on -Werror

Change-Id: I4f1c08bbcaf1ad3a97502cde756a2f42bcece789
Merge "libcpustats: Turn on -Werror"
auto-merger: merge in from aosp/master
fix up merge error