Introduce dd4hep v01-26 to be used when LCG 104 is used.
This is to prepare the update to LCG_104 where DD4HEP v01-26 is used.
I understand we are using the Gaussino gitlab repository because we still need to apply some patches to DDG4 (see DD4hep!1 for list of applied commits to released branch).
Are they all still needed?
While I understand how to update HepMC3 that is fork of the official HepMC repository, it is not clear to me how to do it for DD4hep where the central repository is in GitHub.
I also see an LHCb/DD4hep gitlab repository...