[clang] [libcxx] [llvm] Triple::normalize: Use none as OS for XX-none-ABI (PR #89638)

[YunQiang Su via cfe-commits]

wzssyqa wrote:

@peterwaller-arm half-done. Do *NOT* merge it now. It has still some problem.
See `clang/test/Driver/baremetal-multilib.yaml`.

There is still some `none-unknown`.

https://github.com/llvm/llvm-project/pull/89638