The patch itself looks fine, but I wonder how useful it will be.

A small question about the patch, why this case in the cross_arch function:

+	  x86_64*darwin*)
+	    echo i386

That doesn't look correct.


Back to the more important issue of the usefulness of this patch:

* Why is cross-compiling to OSX useful at all? You still have to test
  if the output of the compilation works, and for that you need
  an OSX system.

* The patch will only help with cross-compiling C code, it won't compile
  resource files (like the NIB file in Python Launcher)

  This is not a problem right now because that project currently contains
  older NIB files that can be used for editting and running, but would
  make it harder to move to the more modern XIB files that were introduced
  with Xcode 4.

* This will make support harder, I already get support questions where
  the answer depends on the way Python was build and that will likely
  get worse with cross-compiling.

* Where would users get the SDK? I'm not a lawyer (or even familiar with
  US law), but the Xcode license seems to indicate that it can only
  be used on Apple systems.