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

[via libc-commits]

lntue wrote:

So I think there are 2 different things: the `test/include/isnan*_test` should test that the *macro* `isnan` works for floating point types (we might add `float16` and `float128` later if required), while `test/src/math/isnan*_test` should test for the entry points `LIBC_NAMESPACE::isnan*` *functions*.  So both have there own merit.

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