[Bug c++/116366] the const specifier is dropped when using member object as template parameter

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116366

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note it is unrelated to member objects too as shown by:
```

template<class T>
auto declval() -> T&;

static int x;

template<auto * M>
using mem_type = decltype(*M);

template<auto * M, typename T = mem_type<M>>
void set_mem(const T& v)
{
        *M = v;
}

static constexpr auto p = &set_mem<&x>;
```