[Bug c++/69967] #pragma GCC diagnostic ignored being ignored for -Wunused-variable in some cases

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69967

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Most likely this warning does not happen until all of the translation unit has
been parsed in.  The variables are not marked as being used.