PyPI doesn't have Apple M1 version

[dgarnier]

Some changes to build locally just using "pip" on an M1 mac, and then maybe also help with the github action, but I don't know if it will work. At least this branch can by build directly by pip or poetry for use in other projects.

[dgarnier]

The issue is that the PyPI version has a "universal2" Mac package that doesn't actually have a universal binary, but an intel binary in it. I'm not sure if these changes will fix the issue, but I suspect they might. Certainly, using the supported "pip wheel" instead of "python setup.py bdist_wheel" is somewhat different. I also removed the homebrew eigen3 version and instead use the linked version in the repo, as homebrew discourages using their builds for redistribution in wheels. If this doesn't work, my suggestion is to use ciwhieelbuild. (I have other codes that use it, and it seems to work.)

[drlukeparry]

Hi Darren, Thank you for sharing these changes. I often build locally on Mac M1, so I don't encounter these redistribution issues directly, although it would be very useful to learn how to maximise compatibility specifically with the M1 platform. I will need time to try this out and understand better the implications during the build process using GitHub actions.