We've not really been using the Focal containerfile, as we move
forward jammy is a better choice for keeping stable as we might find
some new users for it.
Also add binutils to bindep for native bullseye builds (see
Icb0e40827c9f8ac583fa143545e6bed9641bf613)
Change-Id: I22ebe2bbccaec34180e58996b21e47bfc4f36055
