[clang] [Clang][Driver][AArch64] Add support for aarch64-amazon-linux triple (PR #109263)

[Peter Waller via cfe-commits]

peterwaller-arm wrote:

> As the comment specifies, we really should not add new elements to *Dirs arrays in Generic_GCC::GCCInstallationDetector::CollectLibDirsAndTriples.

Thanks for following up again @MaskRay. Forgive me for asking, but I didn't see a clear justification for "why" along side that comment. Only that it is so. I can imagine some justification for the rule, but where do you see the pressure coming from against adding it in this specific scenario? Can it be added in the interim until a proper fix has been identified/made?

Is anyone in a position to fix the config.guess machinery, or suggest a method to reliably detect the triple in LLVM's cmake? Is this merely a matter of adding a test for the existence of a directory in the cmake, or is something more complicated necessary?

https://github.com/llvm/llvm-project/pull/109263