[Bug c++/119699] fnspec for constructors/deconstructors don't say they return this when targetm.cxx.cdtor_returns_this () returns true

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119699

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Also for:
```
class x
{
public:
  x ();
  x (const x&);
  int func ();
private:
  int a;
};

x g ()
{
  return x{};
}
```

We should be able just do a tail call to `x::x()` (but that depends on 67797
which I will be fixing for GCC 16).