extend builder to avoid having to set up trivial dune modules
Assume I want to add an
Operator implementation contained in one header file. If I want to use the
builder I will need to set up a whole dune module with that one header file to do that. It would be nice if I could simply set up a dune subpackage (so setup.py, dune/init.py and dune/mymodule/__init__py) also containing this one header file and still be able to use the whole builder.
This could be achieved by adding an additional header search path to the cmake target.