When opening a demo or example in Qt Creator*, if the demo or example code locates in a ready-only folder, Qt Creator* will copy the code to a writable folder and open from there. This happens more often on Linux* environment because the installation directory is not modifiable.
The issue here is the Qt Creator* did not copy the subdirectories of the demo or example and so it causes the compilation error.
The work-around is to copy the subdirectories manually. In this case of stickman example, by copying the "animations" subdirectory, it solves the issues.