Only build Doxygen docs if dot and Doxygen are present
Only build Doxygen docs if dot and Doxygen are present

Change-Id: I015fe07702cc1061d5efbc98a7f6b3637be4ee3b

advancedtelematic/sota_client_cpp,advancedtelematic/aktualizr,advancedtelematic/aktualizr,advancedtelematic/aktualizr,advancedtelematic/aktualizr,advancedtelematic/sota_client_cpp