[Merge] ~xypron/livecd-rootfs:required_partition into livecd-rootfs:ubuntu/master

[Michael Hudson-Doyle]

Review: Approve

I was a bit scared from the diff that this was going to affect cpc images but I see from looking at the file that this is riscv64 only so fine!
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https://code.launchpad.net/~xypron/livecd-rootfs/+git/livecd-rootfs/+merge/435840
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