OVITO for Windows is typically built using Microsoft's Visual C++ 2015 compiler. However, building it with the MinGW compiler should still be possible too.
More instructions how to build the required dependencies on Windows and OVITO itself
can be found in the file
doc/develop/build_windows_howto.txt after downloading the source code.
The required steps are quite involved, and the available instructions may be insufficient.
Please contact the author if you want to build OVITO on Windows and get stuck.