[llvm] [LLVM][rtsan] Add sanitize_realtime attribute for the realtime sanitizer (PR #100596)

[Chris Apple via llvm-commits]

cjappl wrote:

@nikic or @vitalybuka could we get a merge on this when you get a chance?

Thanks for everyone's review and discussion!

https://github.com/llvm/llvm-project/pull/100596