[libcxx-commits] [libcxx] [libc++][math] Add `constexpr` to `std::fpclassify` (PR #210993)

[A. Jiang via libcxx-commits]

frederick-vs-ja wrote:

> @frederick-vs-ja I'm not sure specifically why the tests are currently failing.

Perhaps I suggested some wrong thing. Clang seems to consider `_LIBCPP_PREFERRED_OVERLOAD` too early (before further resolution), so perhaps we should add the `_LIBCPP_PREFERRED_OVERLOAD` back.

https://github.com/llvm/llvm-project/pull/210993