It seems like this bandaid to avoid some build-system related overrides causes more problems than it fixes.
Let's just deal with reality up-front and hope that https://github.com/python-poetry/poetry/issues/2789 will be fixed at some point.
We should never have to use `format = "setuptools"` since pip can
_also_ handle setuptools packages.
This uses a custom pipBuildHook that removes pyproject.toml in case
there is also a setup.py in the same sources.
