[clang] [llvm] [llvm] Add triples for managarm (PR #87845)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay approved this pull request.

The patch mixes the following changes

* Triple
* llvm/lib/Support/Unix
* clang/lib/Driver

I think we need 3 PRs. The Triple and Support code looks good.

I will have limited internet access between April 20th and May 4th, and my response time may be delayed..


https://github.com/llvm/llvm-project/pull/87845