dockerrpm: prepare source outside docker and just run rpmbuild inside docker Simplifies the rpm build process. We will use platform specific rpmbuild directories and will not clean them and will drop the explicit copy to build directory.

dockerrpm: run docker build process as the current user, not as root Docker can be run by ordinary users if they are in the docker group. The build process would however be run as a root user, only protected by the sandboxing. That caused problems with the shared directory where rpmbuild would be picky about building from sources owned by less privileged users and producing files owned by root. Instead, add a build user with the right uid/gid to the image and run the docker process as that user.

dockerrpm: better handling of specification of docker name