pypardiso breaks native builds on Arm64 architechture (the new Apple silicon)

[ma-sadeghi]

PyPardiso requires MKL, which requires Intel architecture. Two options:

• Distribute platform-specific releases: without pypardiso for macOS, with otherwise
• Remove pypardiso as a hard dependency, but add a warning if the user's not using pypardiso to install it (if they're on Intel)

The latter is easier and probably more maintainable.

[haasad]

@ma-sadeghi Have a look at https://github.com/conda-forge/bw2calc-feedstock/blob/main/recipe/meta.yaml#L27-L29 for inspiration on how you could easily get platform-specific builds with conda-forge (not sure if something similar is possible for pip).
scikit-umfpack is a fast solver that you could use as alternative to pypardiso on osx-arm

[ma-sadeghi]

@haasad Thanks for the pointer! Currenlty, I'm lacking bandwidth to fix this, but it's on my todo list. I'll reopen this not to get lost.