Split build task in Rakefile

This might become a big more cleaner and Makefile like.

Also, since we cannot mount 9p filesystems with write easily (permissions-wise vs. the host, at least) our vagrant-libvirt setup has to write the artifacs to disk (inside the guest) as an intermediate step. If the build task is split up, the fetch can more easily be mixed in between the build and build dir teardown.

Feature Branch: feature/11171-split-rakefile-build-task

Related issues

• Related to #6354 (closed)

Original created by @anonym on 11171 (Redmine)