Install RIOT toolchain on Raspberry Pi

• add jessie-backports, see [here] for details. Quick way add to /etc/apt/sources.list: ´´´ deb http://http.debian.net/debian jessie-backports main ´´´
• to install compiler and openocd run:

sudo apt update
sudo apt -t jessie-backports install gcc-arm-none-wabi openocd