Cleanbuild remote on pi grabs wrong arch lxc image

[lucyllewy]

@kalikiana

What Snapcraft does here is install the same versions of core snap and itself for predictable behavior. Since Snapcraft re-runs itself in the container, an older Snapcraft in the container eg. from apt would lead to potentially unexpected behavior.

but is not the whole point of cleanbuild that it builds in a completely virgin environment with no ties to the host?!