[Merge] ~itrue/livecd-rootfs:add-nemos-support into livecd-rootfs:ubuntu/master

[Isaac True]

Review: Needs Resubmitting

@lool I've spoken with the customer and we'll rename the projects to bring them in line with the Deb way of naming architectures, and the reference descriptions will now be called "qemu-amd64" and "qemu-arm64", rather than "x86" and "aarch64".

I'll adjust the merge proposal.
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https://code.launchpad.net/~itrue/livecd-rootfs/+git/livecd-rootfs/+merge/440173
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