Partially reverts commit 9c5bffcf93183df0756e01f3c4774d2f83688b8e.
The reasoning behind this is that setup.py is intended to strictly consume the Makefile and not be consumed by it. The attempt at using them recursively has caused a number of issues and has rendered Pyosys unusable to some users: See https://github.com/YosysHQ/yosys/issues/5012
Additionally, unlike the previous pyosys installation target, the wheel installation does not respect PREFIX=, only venvs.
For installation inside a venv, the intended method should remain a user manually executing `pip3 install .` instead of relying on the Makefile.
c18f1310a5