Embedding Python on Windows and spawning processes

Hi

After much frustration, I figured out why processes were failing to start when spawned through embedded python code on windows.

It seems that a small workaround is needed on windows in order to spawn new processes:
https://stackoverflow.com/questions/15636266/embedded-python-multiprocessing-not-working

This is very briefly mentioned in the Python documentation:
https://docs.python.org/3/library/multiprocessing.html#multiprocessing.set_executable

I am not sure if the "workaround" has any side-effects or if it could be incorporated into the instantiation of Python specifically for windows?
An alternative would be putting a warning in the documentation stating that this must explicitly be configured in order to spawn processes on windows.

Start with the linked Python multiprocessing.set_executable documentation and the Stack Overflow report, then trace PyO3's Windows-specific embedded-Python initialization and process-spawn entry points. Done means determining whether the workaround is safe to incorporate or documenting the required configuration and its Windows scope.