thanks a lot to @sothix for helping with this!
removed pytest-forked, is not found anymore:
error: target not found: mingw-w64-ucrt-x86_64-python-pytest-forked
use a virtual env to avoid mixup of user with system packages.
remove old workaround for setuptools (SETUPTOOLS_USE_DISTUTILS: stdlib).
fix pip install
use --system-site-packages as a workaround for broken pip install python-cffi.
do not upgrade pip setuptools build wheel
use python -m pytest to use the one from the venv