This was not happening before GCC 12.

Reduced testcase from a Firefox build failure we got in Debian on armhf:

```
#pragma GCC visibility push(hidden)
namespace std { class type_info; }
#pragma GCC visibility pop
#include <typeinfo>
bool foo(std::type_info& a, std::type_info& b) { return a == b; }
```

Compile with `-O2 -D__GXX_TYPEINFO_EQUALITY_INLINE=0` (the define makes the problem appear on all platforms, rather than armhf only)

What happens in this example is that the symbol reference to `std::type_info::operator==` ends up with hidden visibility, instead of default visibility. With GCC 11 and older versions, it would end up with default visibility.

On godbolt:
https://godbolt.org/z/hYKjWGaeq

(Ironically(?), that forward declaration comes from ICU working around an old bug in libstdc++ headers)