Just to link the various pieces together: I think 

https://bitbucket.org/pypa/distlib/src/2d145da7cb42590039fbd56a9ab764d5d4716a98/distlib/wheel.py#lines-53

is the place in distlib that's being breaking pip due to redefining distutils.util.get_platform() as the cross-compile target architecture  rather than the build architecture.

https://docs.python.org/3/distutils/apiref.html doesn't show it as a documented public function, but the commit Ryan linked did introduce a new get_host_plaform() that matches the old behavior; if that became public and distlib used itinstead (conditional on the python version?) that would also be a way to fix the symptom Ryan noted (pip now choosing the wrong wheel to install).

I don't know how the pieces here fit together well enough to now which side should change.

@zooba: adding you to the Cc since it was your comments at https://github.com/python/cpython/pull/11774#discussion_r254461961 that seem to have led to the decision to re-define get_platform, maybe you have some relevant context?