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

[via llvm-commits]

pcc wrote:

We usually only support `__attribute__((no_sanitize("sanitizername")))` as the attribute for disabling a sanitizer.  Some sanitizers have other attributes for disabling them but they only exist for backwards compatibility reasons.

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