Ah.  Reading your second message more closely, you're presumably getting a 'no' there.  Could you double check that 'HAVE_ROUND' is not defined in pyconfig.h?

In that case, what's supposed to happen is that there's a substitute 'round' function defined in Python/pymath.c that gets used.  That's clearly working okay in the Python core, since it looks like your build doesn't fail until you get to the module build stage, and 'round' is used in Objects/floatobject.c in the core.

But I'm guessing that for some reason your Python executable isn't exporting that 'round' symbol that's defined in pymath.c.  I'm not sure why that would be.