aib: If --ostree-repo is specified, use that before exporting the repo
Otherwise the repo will be gone from the image_output dir when we try to pull from it:
Running: sudo mv _build/image_output/ostree-commit/repo cs9-qemu-minimal-ostree.x86_64.repo
Running: ostree pull-local --repo=ostree-repo _build/image_output/ostree-commit/repo