By using microservices it is possible to load tracker related code only if the SDK is given in CMake. This was already implemented for the Polhemus tracker in T22854. A general description of the microservice mechanism can be found here: http://docs.mitk.org/nightly/IGTHowToImplementATrackingDevice.html
... this can be applied to the optitrack and to the claron tracking device which both needs SDKs/libraries and the code is useless if they are not given by cmake.