offload-build should create subvolumes in /var/lib/archbuild
Currently we have ~ 162 subvolumes from offload-build (most likely as the build was aborted
[root@dragon ~]# btrfs subvolume list / | grep offload | wc -l
162
These should be cleaned up automatically using clean-chroots, by changing offload-build to create subvolumes in /var/lib/archbuild.