[Bug libstdc++/70692] No warning when std::function binds a reference to a temporary

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70692

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Bah, it seems that -Wsystem-headers doesn't get turned off again by the

#pragma GCC diagnostic pop