arm64 support

[zcutlip]

Problem

x86-64-only builds present a couple problems for Mac users:

1. We can run the intel builds on macOS for now with Rosetta 2, but Apple has announced an end date for Rosetta. Additionally, this year is the last year for a native intel build of macOS, as the only remaining supported intel Mac is the 2019 Mac Pro.
2. We can't run the x86-64 builds in Linux VMs on a Mac, so we need arm64 builds for that.

Description

It would be great if we could get arm64 macOS and Linux builds.

I believe this would also help support Raspberry Pi users.

Alternatives

Rosetta 2 on macOS is a workaround on that OS, but no alternative exists for arm64 Linux that I know of.

p.s. Thanks for making pls! It's super useful.

[zcutlip]

An additional note: distribution for macOS could be simplified with a universal binary if you wanted to maintain the intel compatibility in addition to arm64.

I'm assuming the rust build system can spit those out, but if it can't, you can do:

$ lipo -create -output ${pls_universal} ${pls_arm64} ${pls_x86_64}

[dhruvkb]

If you could make a PR to add more targets to the build job in CI, that'd be great. We currently have x86_64 builds only but there really is no reason to not support arm64.

pls/.github/workflows/ci.yml

Lines 73 to 79 in 572a9b5

	include:
	- build: linux
	os: ubuntu-latest
	target: x86_64-unknown-linux-musl
	- build: macos
	os: macos-latest
	target: x86_64-apple-darwin

[zcutlip]

I was able to build a universal binary on my Mac without too much trouble (modulo some trouble with package-managed cargo & rustup not wanting to cross-compile).

It does take a few steps as it turns out:

1. build arm64 darwin
2. build x86-64 darwin
3. lipo the two slices

❱ lipo -create target/aarch64-apple-darwin/release/pls target/x86_64-apple-darwin/release/pls -output pls
❱ file pls
pls: Mach-O universal binary with 2 architectures: [x86_64:Mach-O 64-bit executable x86_64] [arm64]
pls (for architecture x86_64):	Mach-O 64-bit executable x86_64
pls (for architecture arm64):	Mach-O 64-bit executable arm64
❱ ./pls --version
pls 0.0.1-beta.9

Conveniently, when you build the arm64 binary, it's ad-hoc codesigned automatically (ad-hoc codesigning or better is required on Apple Silicon), so there's no codesign step required I believe.

I'm thinking through how to integrate this into ci.yml's matrix.os loop, since this requires more/different steps that building on other OSes.

I'll need to give this some more thought because I want to be as minimally intrusive as possible.