[Bug libstdc++/80187] C++ variant should be trivially copy constructible if possible

[ambrop7 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80187

--- Comment #4 from Ambroz Bizjak <ambrop7 at gmail dot com> ---
Oh wait sorry, that doesn't solve it (yet), the variant_storage_byte would
still have a default copy constructor that copies the byte member.