Please fix kde-runtime buildsystem

[Albert Astals Cid]

If kactivities is not found it gives

-----------------------
CMake Error at 
plasma/declarativeimports/plasmaextracomponents/CMakeLists.txt:3 
(find_package):
  Could not find module FindKActivities.cmake or a configuration file for
  package KActivities.

  Adjust CMAKE_MODULE_PATH to find FindKActivities.cmake or set
  KActivities_DIR to the directory containing a CMake configuration file for
  KActivities.  The file will have one of the following names:

    KActivitiesConfig.cmake
    kactivities-config.cmake
-----------------------


It should use a proper macro_log_feature reporting system.

Cheers,
  Albert