[clang] [Clang][Driver][ARM] Forward `-Os` and `-Oz` as multilib flags (PR #149819)

[William Huynh via cfe-commits]

https://github.com/saturn691 approved this pull request.

LGTM, would probably wait for someone who knows more about Clang Driver.

https://github.com/llvm/llvm-project/pull/149819