[test][python] Link Python scipts to build folder

test/python/CMakeLists.txt

+dune_symlink_to_source_files(test_py_gridgeometry.py)
 dune_python_add_test(NAME test_py_gridgeometry
                      COMMAND ${PYTHON_EXECUTABLE} test_py_gridgeometry.py
                      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
                      LABELS python unit)
 
+dune_symlink_to_source_files(test_py_fvproblem.py)
 dune_python_add_test(NAME test_py_fvproblem
                      COMMAND ${PYTHON_EXECUTABLE} test_py_fvproblem.py
                      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}