Native Apple Silicon builds

[corbindavenport]

GitHub apparently now has M1 runners, so it might be possible to generate Apple Silicon macOS builds in the cloud alongside the existing x86 macOS, Windows, and Linux builds: https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners/about-github-hosted-runners#supported-runners-and-hardware-resources

If it works, the install script will need to be updated to download the correct build (and remove Rosetta warnings), because Dart can't compile universal binaries.

[corbindavenport]

Alternatively, it might be possible to compile it on both architectures and then merge them with Xcode's lipo tool, if that can be used from a GitHub action. Then the install script wouldn't have to check the architecture and handle different downloads.