[Bug c++/80635] std::optional and bogus -Wmaybe-uninitialized warning

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Something like __builtin_unreachable() to say "trust me" would be nice, but I
can't think how to do it. So maybe we just want to use a #pragma around the
std::optional destructor to suppress this warning.