Simplify setting up the list of side-by-side artifacts.
Simplify setting up the list of side-by-side artifacts.

There is no need to iterate over all elements over and over again.
Instead, we connect the artifact pair once and then we never have to
encounter it again.

Change-Id: I2fce0c5a9421d3ab898c87b3558c885ca970658c
Reviewed-by: Joerg Bornemann <47777b9406dbddd02a3fdca8341789a013805a11@digia.com>

qt-labs/qbs,gatzka/qt-labs-qbs,qtproject/qt-labs-qbs,gatzka/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,Distrotech/qbs,Distrotech/qbs,villytiger/qbs,qt-labs/qbs,gatzka/qt-labs-qbs,gatzka/qt-labs-qbs,qt-labs/qbs,Distrotech/qbs,qtproject/qt-labs-qbs,villytiger/qbs,villytiger/qbs,gatzka/qt-labs-qbs,villytiger/qbs,qtproject/qt-labs-qbs,villytiger/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,gatzka/qt-labs-qbs,villytiger/qbs,qt-labs/qbs,gatzka/qt-labs-qbs,Distrotech/qbs,Distrotech/qbs,Distrotech/qbs,Distrotech/qbs,qt-labs/qbs,qtproject/qt-labs-qbs