distutils would not only have to check for gcc-4.2 vs. clang, but also needs to strip "-arch ppc" from the compiler flags when it is present and it cannot use gcc-4.2.   Otherwise you cannot build extensions for the 32-bit python installer on OSX 10.7 with Xcode 4.2.

It is sadly enough not possible to create a binary installer that creates a working installation including building of extensions on all supported versions of OSX without adding special-case code to distutils/packaging.

Note that there already is some special-case code to support the universal binary builds on OSX 10.3.9 (which does not have a compiler that can build universal binaries).


W.r.t. the patch: is it really necessary to use a subshell to look for the compiler? I'd either walk os.environ['PATH'] myself or use xcodebuild to locate binaries.