[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 #6 from Christoph Conrads <gcc@christoph-conrads.name> ---
Created attachment 45080
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45080&action=edit
nan-lhs.ii created by GCC 7.3.0 on Ubuntu 18.04 LTS