I just double-checked and I had these R815's updated to Ubuntu 18 LTS, that might be why I'm having issues.
I am not on Ubuntu 18 LTS so I can't check that.
However I did notice I was missing the install build-essential step
You may want to do:
sudo apt install build-essential
and see if the make now works.
sudo apt install ncurses-dev
sudo apt install build-essential
git clone https://github.com/mh0rst/turionpowercontrol.git
cd turionpowercontrol
make