Freshly cloned master branch throws a lot of "Unable to find..." warnings in Qt Creator


I’m relativly new to gui development with C++ and Qt Creator.
I imported the project directly via the git clone feature in Qt Creator. When I build and run the programm I get a rather big stack of warnings I think (yellow bang triangle) and one message looking like an error (red stop sign with bang).
Most of the warnings are saying

Unable to find file for inclusion config.pri

Others say

Failure to find: …/libs/OpenFx/HostSupport/src/ofxhBinary.cpp

and alike
and the error says

Package expat not found

What am I doing wrong. Why are there files missing when I cloned it directly from github? And even more important where do I get these files if not from the projects git repo?


Did you read the instructions (INSTALL…) in the top directory?