[Bug c++/88173] `std::numeric_limits<double>::quiet_NaN()` is not constexpr

[gcc@christoph-conrads.name]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88173

--- Comment #9 from Christoph Conrads <gcc@christoph-conrads.name> ---
nan-lhs.cpp with `float` instead of `double` triggers the same error messages
with `QNaNf` in place of `QNaN`.