lorax: add "System Volume Information" to ESP image

When installation image is written on Windows, it automatically (by the
OS) gets mounted and Windows create "System Volume Information" there.
This obviously means the installation media is modified and then fails
verification.
This is really wrong from the Windows side to automatically modify some
files behind users back. But since we can prevent this with really low
cost by just creating those files ourself and reduce a lot of user
confusion, just do it.

Thanks @pbatard for the help.

Fixes QubesOS/qubes-issues#2051

lorax-templates-qubes/templates/efi.tmpl

@@ -13,6 +13,10 @@ install boot/efi/EFI/*/gcd${EFIARCH_LOWER}.efi ${EFIBOOTDIR}/BOOT${efiarch}.efi
 ##install boot/efi/EFI/*/gcd${EFIARCH_LOWER}.efi ${EFIBOOTDIR}/grub${EFIARCH_LOWER}.efi
 install boot/efi/EFI/*/xen*.efi ${EFIBOOTDIR}/xen.efi
 
+# place those files to prevent Windows recreating them while writing ISO image
+# on Windows (this would break image verification)
+mkdir "System Volume Information"
+install "${configdir}/System Volume Information/*" "System Volume Information/"
 
 # For Secure Boot restore those files (keep in mind 32MB limit on efiboot.img
 # imposed by ISO9660, details in #794):