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

[via llvm-commits]

pcc wrote:

That being said, we normally only add positive LLVM attributes for sanitizers and arrange for the Clang attribute  `__attribute__((no_sanitize("sanitizername")))` to inhibit adding the LLVM attribute (see `CodeGenFunction::StartFunction`). Is there a reason why this approach doesn't work for the realtime sanitizer?

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