[Merge] ~mwhudson/livecd-rootfs/+git/livecd-rootfs:cpc-file-list into livecd-rootfs:ubuntu/master

[Michael Hudson-Doyle]

Finally unclogged focal ubuntu-cpc builds, tested this, made a few small tweaks and will now merge.
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https://code.launchpad.net/~mwhudson/livecd-rootfs/+git/livecd-rootfs/+merge/374332
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