[llvm] [X86] Resolve FIXME: Create cld only when needed (PR #82415)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

Based off #60527 - should we be also detecting use of `std` for a case to add `cld` at function exit? Or can we just rely on the InlineAsm case for now as I think that's the only way that std can occur (in which we should probably explicitly mention std instructions there)?

https://github.com/llvm/llvm-project/pull/82415