21.9: Add new flag to allow GDML to be dumped for Inner Detector systems
GeoDetectorTools have the capability to dump GDML representations of the G4 geometry they build, which is useful for integration with ACTS, for example, but is not currently easy to configure at the top-level.
These changes introduce a new flag to InDetGeometryFlags
which allows this to be simply toggled on and off in a preExec, producing a separate GDML output file for any Inner Detector GeoDetectorTools which are configured.