[Bug libstdc++/91371] std::bind and bind_front don't work with function with call convention

[roland at rschulz dot eu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91371

--- Comment #4 from Roland Schulz <roland at rschulz dot eu> ---
Are there any known issues with the libc++ solution? Otherwise it seems like
the simpler solution than adding a builtin.