Not used by anything on-tree currently. Still, was in dire need
of a clean up. Using pip in .recipes is a big NO NO.
Previous version of this package included, besides setuptools_rust code,
modules for tomli, setuptools, semantic_version, distutils-precedence, and
pkg_resources. All which would override the files from "proper" .hpkg for
those modules, depending on package activation order.
Also, this brings down the size of the package from 1.6 MiB to 47 KiB.
