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

[Chris Apple via llvm-commits]

cjappl wrote:

These all seem like totally reasonable suggestions. I'll wait for Vitaly to chime in with his opinion! I have limited expertise in this area, so I will go with what seasoned hands think are best :) 

If there is a split or a "either way" I would vote for keeping it how it is now, but if there is something that tilts it to the "just clang" side, I am happy to go back and revise the work already done, strip out the attributes etc.

Thanks again for your thoughts on this @pcc. Really appreciate it.

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