[Bug libstdc++/113578] Incorrect sign printed for -nan on RISC-V

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113578

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Oh I need to use constexpr not _GLIBCXX17_CONSTEXPR, because those branches
must not be taken unless the sizes match. Thanks for the CI checks!