For Android they are just using LLVM to generate the binary and deploying it to their emulator (hyperv based I believe). When delivering to Windows they use an

For Android they are just using LLVM to generate the binary and deploying it to their emulator (hyperv based I believe). When delivering to Windows they use an android subsystem and a container to run it. It is a quick and dirty approach, you still would need to put some Windows specific code to access to Windows only SDK such as inking API or Cortana. If you are creating an app from scratch it seems like an universal app with c++ shared code is the way to go