Check for OSTree when building OPC-UA
Check for OSTree when building OPC-UA

OSTree is a build dependency for OPC-UA, so fail at configure time.

Change-Id: Iaa1716593a4f287a9ea1d1422f36361bafec7721

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