[Bug c++/126422] New: differing noexcept incorrectly accepted for a local extern declaration

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126422

            Bug ID: 126422
           Summary: differing noexcept incorrectly accepted for a local
                    extern declaration
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
int noexcept_decl() noexcept(true);

void foo1() {
  extern int noexcept_decl() noexcept(false);
}
```

This is incorrectly accepted. If this was not a local decl, then GCC correctly
rejects it.