[libc] [llvm] [libc][math][c23] Add fmaf16 C23 math function. (PR #130757)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> My understanding was that the backend:* labels were for LLVM code gen backends. 

No, not really. It's fuzzier than that, relevant to the target can spread to many more components and are not localized to the codegen. The auto-labeling rules we have though are too aggressive (in particular many of the test directories are mostly noise)

https://github.com/llvm/llvm-project/pull/130757