Include AArch64 SME builtins to compiler-rt for Bazel.

[sgfuller]

Include the AArch64 SME (Scalable Matrix Extension) source files in the compiler-rt builtins library when targeting aarch64. Added a selection based on OS platform to use either Apple or Non-Apple sources.

[github-actions]

Thank you for submitting a Pull Request (PR) to the LLVM Project!

This PR will be automatically labeled and the relevant teams will be notified.

If you wish to, you can add reviewers by using the "Reviewers" section on this page.

If this is not working for you, it is probably because you do not have write permissions for the repository. In which case you can instead tag reviewers by name in a comment by using @ followed by their GitHub username.

If you have received no comments on your PR for a week, you can request a review by "ping"ing the PR by adding a comment “Ping”. The common courtesy "ping" rate is once a week. Please remember that you are asking for valuable time from other developers.

If you have further questions, they may be answered by the LLVM GitHub User Guide.

You can also ask questions in a comment on this PR, on the LLVM Discord or on the forums.

[sgfuller]

Hello, I'm new to LLVM so your feedback is welcome and appreciated :). As far as I can tell, the ability to get SME sources for non-Android builds right now is missing in the Bazel layer (please correct me if my interpretation is wrong). I'd like to expand this to other ARM 64 platforms. Thanks for your help.