* Enables us to add an optional EFI filesystem
to the anyboot image.
* All existing anyboot behaviour is preserved.
* We still need to figure out how to build bios
and EFI loaders at the same time on x86.
* The tiny "fake ISO" still needs el-torito
alt-boot for the EFI loader to work when burned
to a CD. This makes the EFI loader work when
written to a hard disk / flash drive.