[clang] [clang][AArch64] multilib: fix deduction of "-march=" option (PR #81474)

[Dominik Wójt via cfe-commits]

domin144 wrote:

@MaskRay @petrhosek @smithp35 @mplatings 
Looking at previous reviews for multilib related changes you might be interested.
(ingore the buildkite failure for now. It seems unrelated.)

https://github.com/llvm/llvm-project/pull/81474