Fix a bug where parts of the image are always compiled with
-march=haswell setting.  This breaks even the compilation of lofar-base
further down the line when executed on a non-haswell build host.

This limist the clone to just the branch that is requested and won't
clone an entire repository.

SW-657:  Add the CEP4 optimisation target also to GNUCXX11 and move the CEP4 optimisation target to its own variants file

SW-657:  Add a new build variant for CEP4 optimisation to GNUCXX11_2018 and remove -Wno-terminate c++ option to enable warnings for throw statements in dtors

SW-695:  Make lofar-base and lofar-pipeline rebuildable and add fix for QPID localhost/scu001 change

SW-610:  Change Python3 version to 3.6 since Ubuntu did update Python3 since we modified the Docker file for Python 3.5 last week