macOS Universal Binary support

[hmenke]

Currently we only build macOS binaries on macOS 11 x86_64. These binaries can run on the newer arm64 hardware (M1/M2) but will be emulated within Rosetta 2, which results in degraded performance. Code for x86_64 and arm64 can be generated and packaged into what Apple calls a Universal Binary.

People interested in native support for pairinteraction on M1 or M2 Macs please leave a 👍 on this issue (using the emoji reactions in the bottom left corner of this issue card), so that we can gauge whether it would make sense to invest time and money in the necessary hardware.

[nelsond]

Would definitely be great if pairinteraction could be made to run on Apple silicon.

I quickly tried to build on an M1, but ran into issues since the MKL libraries were not available. I would be happy to invest more time if there was potentially a bit of assistance to get this going.

[seweber]

You can try the commands that we use to build pairinteraction for non-M1 Macs. Instead of installing MKL, we use brew install lapack to obtain a linear algebra library. However, because we do not have access to an M1, I am not sure whether these instructions also work for the M1 architecture. Thus, it would be great if you can let us know. If you find a way to build pairinteraction on an M1, I would be very happy to add it to the documentation.

Adding such instructions to the documentation is perhaps the best we could do for now, because building binaries for M1 is not yet supported by GitHub Actions (according to actions/runner#805 (comment), M1 might be supported some time later this year, hopefully).