[compiler-rt] [compiler-rt][nsan] Add support for nan detection (PR #101531)

[Alexander Shaposhnikov via llvm-commits]

alexander-shaposhnikov wrote:

I don't have a local repro, but based on the provided log - `FT = double`, and the current isnan is actually a macro
that expands to `__builtin_isnan`. I'm not sure why this doesn't compile, but I'd try the ::isnan. If this doesn't work, one can use smth like `bool isNaN(T t) { return t != t; }`

https://github.com/llvm/llvm-project/pull/101531