Add arm64 prebuilds for macOS

[qier222]

Test run: https://github.com/qier222/better-sqlite3/actions/runs/2804599147
build.yml for test: https://github.com/qier222/better-sqlite3/blob/master/.github/workflows/build.yml

I have tested it on my project using Electron 18, works fine.

[mceachen]

This delta assumes the github actions runner arch will be intel--that may not be a safe default, given how you can't even buy intel macos boxes anymore.

Is there a nicer way to do this? Use qemu like we do for alpine? Perhaps make line 73 specific to linux, and make 2 run lines for macos with --arch?

[evanpurkhiser]

This delta assumes the github actions runner arch will be intel--that may not be a safe default, given how you can't even buy intel macos boxes anymore.

Are we worried about the GHA worker being swapped under our feet? I would expect GitHub to give ample notice if they change their macOS workers.

Just my 2c but seems like it would be better to merge this and make everyone in #769 happy than to try and get the workflow highly-future-proof.