> I'm not talking about the standard library obviously.  I don't remember my original use case exactly, but I must have been compiling a C extension on a system and expected it to work on another.

It seems like we are talking about two different things:

* My issue is restricted to the C extensions compiled by Makefile and setup.py: C extensions of the standard libraries
* You are talking about third party extensions: that's out of the scope of this issue, since my issue is about Modules/makesetup.