Use macros to remove CFI information for MAC OS/X

Place allocation macros inline for x86 as the macros aren't/can't
go through the Linux/OSX normalizing macro wrappers.
Switch to clang for OS/X host build thereby enabling -std=gnu++11
and -Wthread-safety. Remove the -Wstrict-aliasing numeric option
as 3 is the default warning level and warning levels aren't
supported by clang's command line.

This builds as far as gtests which fail due to assumptions they
would only ever compile on non-GCC with RTTI.

Change-Id: Id0d83578e9b93b0f6aea5e9b8ddf2815f0dcd8aa
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>