[configs/releng] Fix /root mode

Thanks Izumi Natsuka for reporting this.
Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@gmail.com>

configs/releng/airootfs/root/customize_airootfs.sh

@@ -9,6 +9,7 @@ ln -sf /usr/share/zoneinfo/UTC /etc/localtime
 
 usermod -s /usr/bin/zsh root
 cp -aT /etc/skel/ /root/
+chmod 700 /root
 
 useradd -m -p "" -g users -G "adm,audio,floppy,log,network,rfkill,scanner,storage,optical,power,wheel" -s /usr/bin/zsh arch