[Bug libstdc++/88840] [9 Regression] std::allocator::construct signature might be ill-formed now

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88840

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #5)
> Or maybe hiding it in a constexpr static function
> __use_relocate() would be sufficient, that would look nicer.

Yup, that's what I went with.