Fix tracker building as a subproject

As tracker-miners' -Dtracker_core=subproject option makes use of the Tracker repo, it does leak the tracker_common_dep into tracker-miners, and together with libtracker-miners-common. The dynamic linker seemed to cope with this as both libraries were about the same. This did change recently, breaking CI in tracker-miners.

Avoid leaking the libtracker-common dependency out of the tracker project when building that way.