Change lhcb-dd4hep to have DD4hep use G4 units and add slot with ROOT units
Switch lhcb-dd4hep to use LCG_101x therefore have G4 units. Replace lhcb-dd4hep-g4u by lhcb-dd4hep-rootunits
Requires lcg-toolchains!104 (merged)
Switch lhcb-dd4hep to use LCG_101x therefore have G4 units. Replace lhcb-dd4hep-g4u by lhcb-dd4hep-rootunits
Requires lcg-toolchains!104 (merged)