ludwigschwardt/python-readline — pull request #21 by minrk (2012-10-19 20:53:12+00:00)
Title: only add `-isysroot SDK` if the SDK exists

python-readline will not build on Python.org 3.3 / OS X 10.8, because
distutils.platform gives 10.6 and the 10.6 SDK will not exist.

This follows the same logic in the stdlib, which strips sysroot args for SDKs
that do not exist.