10.8+ when using a universal Python that included a PPC architecture,
such as with a python.org 32-bit-only binary installer.

    In particular, fix extension module build failures when trying to use
    32-bit-only installer Pythons on systems with Xcode 4 (currently
    OS X 10.8, 10.7, and optionally 10.6).
    * Backport 3.3.0 fixes to 3.2 branch (for release in 3.2.4)
    * Since Xcode 4 removes ppc support, extension module builds now
      check for ppc compiler support and by default remove ppc and
      ppc64 archs when they are not available.
    * Extension module builds now revert to using system installed
      headers and libs (/usr and /System/Library) if the SDK used
      to build the interpreter is not installed or has moved.
    * Try to avoid building extension modules with deprecated
      and problematic Apple llvm-gcc compiler.  If original compiler
      is not available, use clang instead by default.

    In particular, fix extension module build failures when trying to use
    32-bit-only installer Pythons on systems with Xcode 4 (currently
    OS X 10.8, 10.7, and optionally 10.6).
    * Backport 3.3.0 fixes to 2.7 branch (for release in 2.7.4)
    * Since Xcode 4 removes ppc support, extension module builds now
      check for ppc compiler support and by default remove ppc and
      ppc64 archs when they are not available.
    * Extension module builds now revert to using system installed
      headers and libs (/usr and /System/Library) if the SDK used
      to build the interpreter is not installed or has moved.
    * Try to avoid building extension modules with deprecated
      and problematic Apple llvm-gcc compiler.  If original compiler
      is not available, use clang instead by default.

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.