cc: toolchain: add support for aarch64-darwin-llvm [BUILD-563]

[jungleraptor]

Adds support for building with the custom llvm toolchain on aarch64-darwin.

Design notes

• Adds aarch64-darwin-llvm toolchain. The llvm-project does not have prebuilt binaries available for clang-14 on arm macs, so we had to build this distribution from source ourselves: Test m1 mac swift-toolchains#14
• Enables treating warnings as errors on macos
• Disables -ffp-contract=on which was made the default in clang-14
• Enables using the llvm distribution clang-format instead of a system install for aarch64-darwin.
• note: on macos coreutils is an implicit dependency since we use realpath in the clang-format scripts.

Testing

• Tested several of our bigger projects on m1 mac
• Tested we didn't break any compatibility on intel mac
• https://github.com/swift-nav/starling/pull/7839
• https://github.com/swift-nav/orion-engine/pull/5906
• https://github.com/swift-nav/orion/pull/5513

[jungleraptor]

I'm not really sure what chained fixups are but it doesn't seem like we need them, and this silences a bunch of annoying linker warnings.

We do need to build with -undefined dynamic_lookup however.

[krisukox]

LGTM