/usr/src/nrelease has the ability to build the new ‘live’ CD iso images. Listed here is what Matt Dillon listed as possible make targets in that directory:

“release: This will do a full buildworld and buildkernel (GENERIC)
with the current source tree, then generate the release
ISO and directory structure in /usr/release.

quickrel: This will do a ‘quick’ buildworld and buildkernel (i.e.
-DNOCLEAN) and then generate the release ISO and directory
structure in /usr/release.

realquickrel: This is even faster. It assumes that the buildkernel and
buildworld have already been done and just generates the ISO
directory structure and ISO file in /usr/release.”