MF10: r323900

• Akin r302691 in head, synchronize the build stripping for the disc1 image with that of the bootonly image (but similarly modulo games and groff(1)) as the amd64 disc1 image is overflowing. This also removes the defunct WITHOUT_ATF.
• Remove the misspelled WITHOUT_INSTALLIB (also in place with correct spelling, i. e. WITHOUT_INSTALLLIB) from the bootonly image build stripping.

This is a direct commit to stable/10 as the corresponding knobs have
different names in head and counterparts to e. g. MK_DEBUG_FILES and
MK_TESTS default to off in stable/10 in the first place.

Approved by: re (implicit)