In a local install, we don't have udev running, so the setupSCSI step
will hang if it tries to probe for logical volumes (lvm2 uses udev).

A local install is used to test the installer (drakx_in_chroot) and to
build the Live ISOs (draklive2), and in both cases we don't really want
the install to be affected by the hardware of the host system. Skipping
the setupSCSI step means $o->{fstab} contains no entries, so we add a
fake entry for our chroot, to allow us to pass the subsequent check
that we have a root partition.

This fixes a bug introduced by commit c253952df2. That was only supposed
to select GPU firmware packages, but actually selected driver packages as
well.

This avoids selecting the wrong arch when building on an EFI system.