We can stop iterating once we've found the DOF section.

Submitted by:	Fedor Indutny <fedor@indutny.com>
Convert a couple lingering NO_FORTH conditionals to test MK_FORTH.
Use explicit --output-target to set EFI file format

According to objcopy(1) --target is for use where the input and output
formats are the same ("no translation"). In practice it does detect the
input format in any case, but be explicit that we're specifying the
output format as we are translating from ELF to EFI PE format.

Sponsored by:	The FreeBSD Foundation
Update comment: only one file in the FAT file system EFI boot image

Sponsored by:	The FreeBSD Foundation