Use the "freenas-tarball" makefile target to create a tarball for
installation on FreeNAS 8.3 or 9.2. The tarball must be made on the
corresponding FreeBSD system (since FreeNAS has no installed compiler).

To install the tarball on FreeNAS you will need to login as root and:

    cd /
    mount -o rw -u /
    mount /cfg
    tar xzf freenas-tarball.tar.gz
    unmount /cfg
    mount -o ro -u /