i previously added this just for kicks, but it's not
actually needed; gnat isn't used on fam15h boards so
lbmk doesn't even use it (it's disabled).
in fact, i tested lbmk with crossgcc_ada handling
taken out, but with said patch; i still got build
errors with gnat anyway, on that old coreboot
revision (but gnat isn't needed there anymore).
Signed-off-by: Leah Rowe <leah@libreboot.org>