[Bug libstdc++/66146] call_once not C++11-compliant on ppc64le

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66146

--- Comment #36 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Attribute unused, not attribute used.

I'll fix it shortly.