.gitlab/ci/build-host.sh:
Add script to be run in a container with access to qemu.
It is a slight modification of arch-boxes' build-host.sh script to cater to the specific archiso requirements.

.gitlab/ci/build-inside-vm.sh:
Add script to be run in virtualized environment, established by build-host.sh.
This script builds the actual archiso profiles and creates checksum for the resulting image files.