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

[Fangrui Song via cfe-commits]

MaskRay wrote:

Some older `ToolChain`s were probably contributed with a lot of `CmdArgs.push_back` uncovered by tests. They are not good examples to follow. For new `ToolChain`s, we ensure that all constructed `CmdArgs.push_back` are covered. This allows refactoring by someone who is unfamiliar with your usage pattern.

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