[problem] Improve symlink slide.

slides/problem.md

@@ -730,6 +730,8 @@ dumux_add_test(
 Extra: Create linked parameter file in `build-cmake` folder, separately add executable and set compile definitions for an executable:
 ```cmake
 dune_symlink_to_source_files(FILES "params.input")
+# or: add_input_file_links()
+
 # using tpfa
 add_executable(test_2p_incompressible_tpfa EXCLUDE_FROM_ALL main.cc)
 target_compile_definitions(