Do not build unused KWSys SystemTools
Do not build unused KWSys SystemTools

We have no uses of SystemTools, so do not tell KWSys to build it.
This also leaves RegularExpression unused, so drop that too.

ellert/CastXML,bradking/CastXML,thewtex/CastXML,bradking/CastXML,iMichka/CastXML,CastXML/CastXML,ellert/CastXML,CastXML/CastXML,thewtex/CastXML,CastXML/CastXML,bradking/CastXML,thewtex/CastXML,iMichka/CastXML,ellert/CastXML