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

[Isaac True]

aarch64 currently maps to the arm64 EFI QEMU image - my plan was to do exactly what you suggested and have SUBPROJECT=nxp-s32g2 for board-specific platforms.

We could rename aarch64 to qemu or something
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https://code.launchpad.net/~itrue/livecd-rootfs/+git/livecd-rootfs/+merge/440173
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