[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 #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Or more accurately, non-(x86-*-gnu), since x86 with musl libc has the same
problem as non-x86 glibc.