Build artifacts (static libraries, in this case) are not compatible, but the built binaries are.

This may be a reasonable argument for not updating distutils's support in minor versions (and I'm totally happy to just stop updating distutils period - see the recent distutils-sig discussion for more context). If it had been raised before 3.6.3 was released then I'd have switched it back (or at least swapped the order, so if v140 was found then it would use that first and fall back on v141). Now it's done, I'm not sure whether it hurts more to change it again in 3.6.4 or not...

The immediate workaround is to set DISTUTILS_USE_SDK and run in a VS 2015 command prompt, which will bypass all the search logic. Better to rebuild the static libraries with v141 as well, but I know that's not trivial or always feasible. Alternatively, build with Python 3.6.2 or earlier - until we get the ABI stability properly figured out, that's still the best way to ensure compatibility with older releases.

I'll give the change back some more thought.