[libc-commits] [libc] [libc][math] implement `signbit` and math macro unit tests (PR #97791)

[Petr Hosek via libc-commits]

petrhosek wrote:

FYI I have a PR #98274  for the `isnan*` tests in `test/src/math`.

https://github.com/llvm/llvm-project/pull/97791