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

[Fangrui Song via cfe-commits]

MaskRay wrote:

#90734 provided a release note. 

The `armv7m-none-eabi` example can probably be copied as an example to improve the commit message/description.

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