Python 3.10 prints a warning when it sees `distutils` used, so let's
avoid using `distutils` in the "common Mach code" that runs on every
Mach call.

Note that this change will also fix the `SetuptoolsDeprecationWarning`
that shipped on `setuptools>=58.3.0`, since our usage of `distutils` was
calling a `setup.py install` under the hood.

Differential Revision: https://phabricator.services.mozilla.com/D137499