[Bug bootstrap/83102] go bootstrap error in ast-dump.cc due to __is_invocable failure

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83102

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #0)
> struct Import_init_lt {
>   bool operator()(const Import_init* i1, const Import_init* i2)

This function needs to be const

>   {
>     return i1->init_name() < i2->init_name();
>   }
> };