[llvm] [LLVM][rtsan] Add LLVM nosanitize_realtime attribute (PR #105447)

[via llvm-commits]

pcc wrote:

Thanks, I didn't see that discussion.

Re 2: this can be accomplished via an API, no? You can provide functions such as `void rtsanMarkAsNonblocking(Function *F);` and `void rtsanMarkAsBypass(Function *F);` and clang and other frontends can call it.

Re 3: we can always defer adding the attribute until/unless the planned functionality is actually implemented.

But I don't have a strong opinion. If @vitalybuka is fine with this being LLVM attributes it's fine with me as well.

https://github.com/llvm/llvm-project/pull/105447