gtk4: Build fails when not --enable-debug build
In a build without --enable-debug gtk4-client's menu_entry_set_visible() is needed, but not available. It's not only within #ifndef FREECIV_DEBUG, but also larger #ifdef MENUS_GTK3 which is never defined in the current codebase.
In a build without --enable-debug gtk4-client's menu_entry_set_visible() is needed, but not available. It's not only within #ifndef FREECIV_DEBUG, but also larger #ifdef MENUS_GTK3 which is never defined in the current codebase.