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 redundant MK_LLDB.

This is a direct commit to stable/11 rather than a MFC of r302691 as
the the disc1 image stripping previously has been directly modified
in stable/11 by r303027.

Approved by: re (gjb)