Hi Lennart
Your link doesn't point to a file but to a repository. Can you please provide the whole file? Also please go to the Arduino IDE preferences and enable the checkbox which says "Verbose Output during ... compilation" and then please add the resulting log to this post. Also please add the content of your Tools menu configuration: especially the board type is important.
Without this information we have to do a lot of speculation to help you.
KR, Dani