beast: require gummiboot

This is not the right place, but OE-core lacks an 'EFI" MACHINE_FEATURE

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
linux-dominion 3.13: disable USER_NS for beast

kdbus build breaks because it's USER_NS unsafe :(

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>