the --nuke option in ifdtool will be used instead, to nuke
the ME regions in specific rom sets (and cbfstool will be
used to delete mrc.bin files from rom sets)

the new method being implemented is heavier on disk io, but
simplifies lbmk, and disk io could still be optimised in
the following ways:

* when copying roms from boards with ME in them, use
  ifdtool --nuke to get filename.rom.new, and *move* (not copy)
  filename.rom.new to the new destination (for use with tar)

* possibly modify ifdtool to make efficient use of mmap for
  disk i/o; it currently loads entire roms into an allocated
  buffer in memory

e.g.

./ifdtool --nuke me coreboot.rom

this will be used by rom release build scripts, to scrub
stuff like intel me from the rom

previously, it was always initialised, but now it's only
initialised if '?' is used on a mac address character in
command `setmac`

this is done by simply moving mac address character
randomisation to a separate function

I will be using this function elsewhere, and in general
I want this to be usable for lots of programs.

the error would have never been triggered, because it never
went over 11, but if this code were to be copied elsewhere,
it would be problematic

If one of the checksums was valid, but the other was not,
errno would be set to E_CANCELED, but then the buffer would
be modified anyway; this is acceptable behaviour, and errno
would later be reset writing the GBE file, which is done
only on the condition that the buffer was modified, but
it's also a good idea to reset it here just in case.

This is not a bugfix, and no behavioural changes will be
observed by the user, but this may *prevent* a bug in the
future, so let's pre-fix that bug now.

These boards are near-identical, this appears to suffice.

New x230edp_12mb target uses the
https://review.coreboot.org/c/coreboot/+/28950 patchset to add an
X230_EDP target to the default coreboot branch.
Consequently the "fhd" coreboot branch is no longer needed and has
been safely removed.

in any C program, main() should not contain detailed logic.

ideally, the main() function should only be a skeleton, showing
the overall logic flow of the program. split writing gbe files
into a separate function, to satisfy this criteria.