[C++] Use bash to run doxygen script
[C++] Use bash to run doxygen script

* Run run_doxygen.sh script from external bash in order to
  avoid problems because of missing execute mode bits.

Change-Id: I95e4eb0f255f65a3dd4950162d4c6fdf1299b459

bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,clive-jevons/joynr