[Bug libstdc++/91057] Data race in locale(const locale&, Facet*) constructor

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91057

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Sorry for not testing on a target that defines _GLIBCXX_LONG_DOUBLE_COMPAT.
Your patch is approved for trunk, please go ahead and commit it.