[Bug libstdc++/103655] "x" does not exist on windows and dos

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103655

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
"We implemented this C11 feature a while ago and backported it to all OSes"

That suggests it should become available everywhere, no?