vtkModule: support module sources outside of the project
The file(RELATIVE_PATH)
computation for such modules ends up also
moving it out of the binary tree in the same way. Instead, reroot these
paths to be under the current binary directory.
A proposed alternative to !8123 (closed). I think this is the root cause of the issue you're seeing. The description of the scenarios is just confusing; instead just describe the problem and fix it in a straightforward way.