This enables the use of "-d generic-efi" device with buildarmimg.
I don't think the resulting image boots, as we still don't generate any .efi file, but the image does look correct otherwise.
- Partition 1: From 0% to 512 MB, marked as ESP (EFI-system type), gets mounted at /boot. It is /boot, because it seems EFI on ARM can't load kernels from outside the ESP/EFI partition.
- Partition 2: From 512 MB to 100%, default root filesystem, gets mounted at /.
TODO: We still need to add a .efi file. Either add a precompiled version via a package (could be boot-generic-efi) or find a way to actually generate it via the tools (requires access to efivars in the systemd-nspawn).
Signed-off-by: Dan Johansen email@example.com