This adds the ability to patch setuptools (and pip), and adds 3
reproducibility patches from Debian[1].
(003-PKG-INFO-output-reproducible.patch addresses the issue identified
in #9039.)

The patching is not perfect, in that the patches are applied to
setuptools and pip after they have been installed, since they are
installed from wheels which are already "precompiled".

Also, patching for the host install cannot be updated in place, for
example if a patch is added or removed.

[1]: https://sources.debian.org/patches/python-setuptools/40.8.0-1/

Signed-off-by: Jeffery To <jeffery.to@gmail.com>