by removing unwarranted assumptions that clang compiler chain
cannot handle ppc (the driver passes off ppc compiles to gcc).
Mock the behavior instead.
tailoring for universal builds by factoring out common OS X-specific
customizations from sysconfig, distutils.sysconfig, distutils.util,
and distutils.unixccompiler into a new module _osx_support that can
eventually also be used by packaging.