Commit 79c0173 ("[build] Create util/genfsimg for building
filesystem-based images") introduced the new genfsimg, which lacks the
-l option when building ISO files. This option is required to build
level 2 (long plain) ISO9660 filenames, which are required when using
the .lkrn extensions on older versions of ISOLINUX.
Signed-off-by: Michael Brown <mcb30@ipxe.org>