There is a check to be sure no system python is in the path
on windows to be sure deps do not accidentally build against it.
The problem arises on certain versions of windows that ship a
python.exe that just opens up the MS store to download their
python version. The check takes this to be a real python
installation and refuses to build.
This change fixes the issue by looking for pythonw.exe which a
real python install would have, but the MS store opening one that
windows ships (as of now) would not.
fe988f6c7f