Crossplatform solution for changing build directory

Created by: TheKnarf

I need to change to build directory for using create-react-app.

In issue #3824 (closed) it was recommended to add a postbuild step:

  "postbuild": "cp build/* restapi/wwwroot"

That works, but pushing it a colleague working on windows started complaining that the build now crashes on his computer (since mv is not crossplatform).

Is there any way of doing this in create-react-app now in 2019 without ejecting?