Change coverity build settings from j2->j4

.dd4hep-ci.d/coverity_scan.sh

@@ -9,5 +9,5 @@ mkdir build
 cd build
 cmake -D DD4HEP_USE_GEANT4=ON -D DD4HEP_USE_BOOST=ON -DBoost_NO_BOOST_CMAKE=ON -D DD4HEP_USE_LCIO=ON -D BUILD_TESTING=ON  -D Geant4_DIR=$G4INSTALL/lib64/Geant4-10.2.2 -D DD4HEP_USE_CXX11=ON -DCMAKE_BUILD_TYPE=Release -DROOT_DIR=$ROOTSYS -DCMAKE_CXX_FLAGS="-fdiagnostics-color=always" .. && \
 export PATH=/cov-analysis-linux64/bin:$PATH && \
-cov-build --dir cov-int make -j2 && \
+cov-build --dir cov-int make -j4 && \
 tar czvf myproject.tgz cov-int