Please support MSYS2 MINGW64

When I saw the submodule /ETEngine/Engine/third_party/gtk/GTK-for-Windows-Runtime-Environment-Installer I immediately know your project doesn't support MSYS2 MINGW64. Because on MSYS2 MINGW64, this submodule is absolutely not needed as we have packages for GTK3 and GTK-for-Windows-Runtime-Environment-Installer is indeed made using MSYS2's GTK3 packages.

[Illation]

The reason I put more effort into compiling with MSVC instead of MSYS2 is because most game developers are used to working with Visual Studio. Mid term I plan on discontinuing use of gtk for UI anyway, to a large extend because it is such a hassle building it for windows, and I will be using the engines internal UI system based on RMLui. Do you have need for MSYS2 outside of helping with compiling GTK?