bc needed for mesh installs

src/freedombone-image-customise

 chroot "$rootdir" apt-get install -y iptables dnsutils net-tools network-manager iputils-ping
 chroot "$rootdir" apt-get install -y libnss-mdns libnss-myhostname libnss-gw-name nano man ntp
 chroot "$rootdir" apt-get install -y locales locales-all debconf wireless-tools wpasupplicant
-chroot "$rootdir" apt-get install -y usbutils cryptsetup zsh pinentry-curses iotop
+chroot "$rootdir" apt-get install -y usbutils cryptsetup zsh pinentry-curses iotop bc
 
 sed -i "s|#host-name=.*|host-name=${PROJECT_NAME}|g" $rootdir/etc/avahi/avahi-daemon.conf
 sed -i "s|host-name=.*|host-name=${PROJECT_NAME}|g" $rootdir/etc/avahi/avahi-daemon.conf