[llvm] [TargetParser] Normalize "aarch64-amazon-linux" to "aarch64-amazon-linux-gnu" (PR #140070)

[Paul Osmialowski via llvm-commits]

pawosm-arm wrote:

> We don't want to encourage 100+ Linux distros that customize the "vendor" component to add new elements to `Generic_GCC::GCCInstallationDetector::CollectLibDirsAndTriples`.

This is a different situation. We are talking about one particular distribution for which the exception has been already made, yet incompletely, as it covered x86_64 only. I doubt it is in anybody's interest to revert that, but it is also damaging LLVM's architectural neutrality if it cannot cover the other architecture this distribution is available for.

https://github.com/llvm/llvm-project/pull/140070