[llvm] [AArch64] Fix SVE callee-save layout for nounwind functions on Windows (PR #156467)

[Benjamin Maxwell via llvm-commits]

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

LGTM, but I'd wait for someone that works on the Windows side to approve. 

"code makes the assumption that CFI is available" => "makes assumptions that only hold when NeedsWinCFI is true"? AFAIK, it's not dependent on the CFI, but changes that only happen when using Windows CFI (such as reversing the callee-saves). 

https://github.com/llvm/llvm-project/pull/156467