Cross-compile

Cross-compiling would be much more efficient than the current approach of 3x pipelines. It would also enable easier debugging of build issues.

Some resources:

https://github.com/mxe/mxe
https://itk.org/Wiki/ITK/Cross_Compiling#Building_the_ToolChain_for_Windows
https://github.com/tpoechtrager/osxcross