The firmware uses DAVE CE to configure and generate code for the hardware abstraction. DAVE can be downloaded from Infineon's website, however it isn't needed for just building.
Install dependencies on Ubuntu by running:
sudo apt-get install gcc-arm-none-eabi binutils-arm-none-eabi gdb-arm-none-eabi
Install Meddela by following the instructions in Meddela's README file:
https://github.com/CodileAB/meddela
Now run make to build:
make -j4 NODE_ID=0x11