About 25 formula in homebrew/core pass `--install-lib` to `python3` in
addition to `*setup_install_args` in order to ensure that all files are
installed into the formula's prefix rather than into a `site-packages`
directory in Python's keg.
Let's simplify these formulae by also adding the appropriate
`--install-lib` flag to `setup_install_args`.
c9af8a632d