Add `osx-arm64` to the default `RuntimeIdentifiers`

[alexrp]

Depends on: ziglang/zig#8680

[alexrp]

I think this will be fixed in Zig 0.8.1.

A ton of work has been done on Zig's self-hosted linker for 0.9.0, but it's still unclear how much of that will be backported to 0.8.1. So this might get pushed to v4.0.

[alexrp]

Still getting MissingMainEntrypoint for library projects with Zig 0.8.1.