Disable the makeoption with MFS_IMAGE= set as we don't ship that file
and it thus breaks the default build.   You can still use various other
ways (tools) to embedd the image after the kernel build.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272216 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f