When a Python package is installed from source (i.e. using setup.py)
into a custom location (with --home), setuptools may want to create a
site.py file in the custom location. This file is created based on the
source code of site-patch.py, a file bundled with setuptools.

Because the normal OpenWrt setuptools package does not contain Python
source code, this file is missing and the installation will end with an
error.

This copies site-patch.py to site-patch.py.txt so that it will be
included in python3-setuptools, and patches setuptools to look for this
file.

See https://github.com/openwrt/packages/issues/12223

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

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>