Arch-specific builds, aarch64 support

Arch-specific builds, aarch64 support

Only x86_64 machines (i386, i686 etc.) use BIOS and have a 'syslinux'
package (currently a dependency of ipa-deployer).

Make ipa-deployer produce arch-specific binaries, adding support for
AArch64 architecture:

- syslinux should be a build dependency only on x86_64;
- diskimage-builder provided by CentOS repos is too old to properly
  support AArch64, rely on PIP to install a working version;
- add EFI system partition (ESP) handling requirements (util-linux,
  dosfstools, gdisk);
- DIB elements: AArch64 requires block-device-efi;
- iso-image-create: Add support for creating EFI images (new args
  "-e", "-E" may be used to specify the path to efiboot.img,
  respectively the EFI directory), handle syslinux only
  on x86, bail if mkisofs fails;
- enable EFI support for x86_64 image too;

Change-Id: Id37164d5eadf5729b8aeb6da0617d3310ba1109b
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>