build as C++ the normal way

Instead of building with $cc and linking a C++ standard library
where needed, build with $cxx, which takes care of that for us.

This lets us use threadsafe statics to check for Haswell support
once, rather than the platform-specific versions we use today.
(Threadsafe statics tend to need helpers from the library.)

Change-Id: If71eb4b6223b36ac6b9c6e587e1614020de5f291
Reviewed-by: Brian Osman <>
Commit-Queue: Mike Klein <>
12 files changed