Fixes of HepMC3 nightlies (small MR)

In this MR:

• fix the compilation of EvtGen in HepMC3 branch

Generators/EvtGen_i/CMakeLists.txt

@@ -27,6 +27,7 @@ atlas_disable_as_needed()
 # Component(s) in the package:
 if (HEPMC3_USE)
 atlas_add_library( EvtGen_iLib
+                   src/EvtInclusiveDecay.cxx
                    PUBLIC_HEADERS EvtGen_i
                    DEFINITIONS -DEVTGEN_PYTHIA -DEVTGEN_PHOTOS -DEVTGEN_TAUOLA 
                    INCLUDE_DIRS ${Boost_INCLUDE_DIRS} ${HEPPDT_INCLUDE_DIRS} ${PYTHIA8_INCLUDE_DIRS} ${PHOTOSPP_INCLUDE_DIRS} ${TAUOLAPP_INCLUDE_DIRS}  ${EVTGEN_INCLUDE_DIRS} ${ROOT_INCLUDE_DIRS}