Update Herwig7HepMC.cxx to define legacy preprocessor directiv
Should fix https://its.cern.ch/jira/browse/AGENE-2091
Tag @ewelina @cgutscho @jchapman
Best regards,
Andrii
Should fix https://its.cern.ch/jira/browse/AGENE-2091
Tag @ewelina @cgutscho @jchapman
Best regards,
Andrii