updateUID fails if user home directory was not created

As [best practice](https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#user), non-root users are created as system users without a home folder. `updateUID.Dockerfile` will fail when used with such images, because it tries to chown the non-existing home folder.

We could either skip chowning or create the home folder. The latter would be useful since vscode seems to use the remote user home folder for its own setup.