Add errors for nonexistend include directory or missing path dependency

[mrogenmoserTT]

No description provided.

[fischeti]

I think we already talked about this, and I just wanted to write down a current issue:

Bender does not consider targets correctly. For instance, an include directory that is guarded by a target and does not exists (yet):

  - target: missing_folder
    include_dirs:
      - missing_folder/include
    files:
      - missing_folder/my_module.sv

throws an error at the moment even if missing_folder is not specified as a target