Workflow improvement we can do for theia (and perhaps all projects being built):

• beyond just doing a cleanWs(), we could also agressively purge content in these places:

• /var/lib/containers/
• /usr/local/share/.cache/yarn/
• /home/hudson/.local/share/containers
• /home/hudson/.cache/yarn/
• /mnt/hudson_workspace/workspace/CRW_CI/* (or maybe just crw-theia-* jobs?)
• various files/folders in /var/tmp and /tmp

I'd suggest reporting `df -h` before and after cleaning, so we can see how effective this is.