Build and provide ARM64 Linux binaries

[bradleymackey]

• Linux builds with Docker are now built using the static Linux SDK from Apple, which statically links Musl into the swiftlint binary.
• Unfortunately, SwiftLint is inherently dependent on shared libraries, so it's not possible at the moment to produce a fully statically linked build. Hosts will need to ensure they have Swift runtime dependencies available. Alternatively, they can run SwiftLint from a Docker container, which bundles all the required runtime dependencies.
  • The aim of this change is to statically link libc (reducing the burden on the host environment to have exactly the correct glibc version).
• Add an ARM64 build to the build artifacts and include this in linux release arifacts and the cross-platform artifact bundle.
  • The artifact paths of the original amd64 binary are unaffected, and the new arm64 binary is named swiftlint_arm64, located in the same directory as the amd64 binary.

[SimplyDanny]

Looking forward to this!

To test the build you could make the docker.yml workflow trigger in pull requests.