[llvm] [LLVM][Clang][AArch64] Implement AArch64 build attributes (PR #123990)

[Hans Wennborg via llvm-commits]

zmodem wrote:

We're seeing significant binary size increase in Chromium after this. I haven't dug into the change yet, but is that something to be expected?

https://github.com/llvm/llvm-project/pull/123990