Since cmake 3.5, I get the following warning every time kcoreaddons_desktop_to_json is called:
"Calling kcoreaddons_desktop_to_json() without DEFAULT_SERVICE_TYPE or SERVICE_TYPES is
deprecated!"
The documentation of kcoreaddons_desktop_to_json recommends that the macro be
used with either DEFAULT_SERVICE_TYPE or SERVICE_TYPES set.
From what I read in [1], DEFAULT_SERVICE_TYPE is used if the macro is called
without neither of the arguments above. So adding DEFAULT_SERVICE_TYPE looks
like the right way to silence the warning.