Fix random error "No space left on device".
For documentation, see
https://openbuildservice.org/help/manuals/obs-user-guide/cha.obs.build_job_constraints.html
For a case on OBS forum, see
https://forums.opensuse.org/t/obs-build-build-vm-line-427-echo-write-error-no-space-left-on-device/140717