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

[via llvm-commits]

pcc wrote:

> Where would such a function live? Can you point me in the direction of other similar functions?

Functions like this would normally be under `llvm/lib/Transforms/Utils`. You can look at existing inclusions of headers in `llvm/Transforms/Utils` under `clang/lib/CodeGen`.

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