add freebsd multi-user installer

[Mic92]

Depends on #13717

Service starts correctly:

[root@nixbsd ~]# service nix-daemon status
nix_daemon is running as pid 823.

PATH script seems to be reset by something:

[root@nixbsd ~]# echo $PATH
/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/root/bin

Current work around is doing this:

root@nixbsd:~ # unset __ETC_PROFILE_NIX_SOURCED
root@nixbsd:~ # set +x
root@nixbsd:~ # . /etc/profile
root@nixbsd:~ # echo $PATH
/root/.nix-profile/bin:/nix/var/nix/profiles/default/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/root/bin

I assume this is not a bug in the script per se but something in freebsd doing this.

[Mic92]

Figured it out:

root@nixbsd:~ # cat /root/.profile
#
HOME=/root
export HOME
#PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:~/bin
export PATH
TERM=${TERM:-xterm}
export TERM
PAGER=less
export PAGER

# set ENV to a file invoked each time sh is started for interactive use.
ENV=$HOME/.shrc; export ENV

# Query terminal size; useful for serial lines.
if [ -x /usr/bin/resizewin ] ; then /usr/bin/resizewin -z ; fi

# Uncomment to display a random cookie on each login.
# if [ -x /usr/bin/fortune ] ; then /usr/bin/fortune -s ; fi

I would like to address this issue in a different PR.
Users could for now source profile.d manually to their own .profile.

[dpulls]

🎉 All dependencies have been resolved !