[Bug libstdc++/70298] std::call_once hangs on second call if first threw an exception

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70298

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
PR66146 is non-x86, whereas this fails on x86 too. It's possibly related
though.