Release AArch64 for macOS instead of x86-64

[AustinWise]

For the last several release builds the macOS x86-64 build has failed. See this release for example. The reason is the SASS C library is being built for AArch64 while Cobalt is being built for x86-64. Example error message:

note: ld: warning: ignoring file '/Users/runner/work/cobalt.rs/cobalt.rs/target/x86_64-apple-darwin/release/deps/libsass_sys-2120902d259b8636.rlib[68](base64vlq.o)': found architecture 'arm64', required architecture 'x86_64'

Rather than figuring out how to fix the x64 build for macOS, I have switch the build to AArch64. I confirmed in my fork that CI builds and that the resulting binary at least can start up.

The reasons for switching the target for macOS rather than trying to fix x64 include:

• x64 was already broken and this was a 1-line fix to add an architecture for macOS.
• The SASS library is deprecated (see RUSTSEC-2021-0136: sass-rs has been deprecated #1050) and archived on GitHub, so if fixing the build problem required changing the upstream, we would have to fork the library.
• AArch64 Macs began selling almost 5 years ago, so at this point many macOS users can probably run AArch64 binaries.

[epage]

Thanks for pointing this out!

I've instead done a separate push as I did a general update to my template for pre-built binaries.

[AustinWise]

Thanks, looks good!