Build the program with Qt5's qmake and make, then run with ./RayTracer (or just open the .pro project file in Qt Creator with Qt 5.9.2 and run there).
If the compiler can't find Eigen, it's likely missing the conanbuildinfo.pri file. Make sure the build directory (./build) and where the file is expected to be in the .pro file match up.
Prerequisites:
sudo apt install build-essential qtbase5-dev qt5-qmake qtbase5-dev-tools cmake qtcreator clang-format cppcheck
pip install conan pre-commit cpplint