[clang] [llvm] [AArch64] Add initial support for -mcpu=olympus. (PR #132368)

[Jonathan Thackray via llvm-commits]

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

LGTM. (apologies for delay; in hospital in Oxford visiting my Dad, but he's gone back to sleep now)

https://github.com/llvm/llvm-project/pull/132368