[clang] [llvm] [llvm][Triple] Add `Environment` members and parsing for glibc/musl parity. (PR #107664)

[YunQiang Su via cfe-commits]

wzssyqa wrote:

> My understanding is that all of these `musl*` environments have been added to GCC and LLVM on an as-needed basis for toolchains, not necessarily because musl itself needs them.

Do you have interesting to add them to GCC? I guess we need to add config.sub/config.guess first.

https://github.com/llvm/llvm-project/pull/107664