Fix NativeMenu layout direction on macOS, add extra check for Windows menu.

[bruvzg]

Fixes #89496 and #89273 (comment)

[akien-mga]

Thanks!

[akien-mga]

I'm getting this build error with mingw:

platform/windows/native_menu_windows.cpp: In member function 'virtual int NativeMenuWindows::add_item(const RID&, const String&, const Callable&, const Callable&, const Variant&, Key, int)':
platform/windows/native_menu_windows.cpp:292:40: error: invalid conversion from 'const WCHAR*' {aka 'const wchar_t*'} to 'LPWSTR' {aka 'wchar_t*'} [-fpermissive]
  292 |         item.dwTypeData = label.ptrw() ? (LPWSTR)label.ptrw() : L"";
      |                           ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                                        |
      |                                        const WCHAR* {aka const wchar_t*}

It's not in the log but there's also the same pattern further down:

952:            item.dwTypeData = label.ptrw() ? (LPWSTR)label.ptrw() : L"";

We really need to add a mingw build to CI :)

[bruvzg]

#89513 should fix it (also more readable).