Fix unused variable in dqEfficiency.cxx (#352)

Author: ktf

PWGDQ/Tasks/dqEfficiency.cxx

@@ -83,9 +83,14 @@ void DefineHistograms(HistogramManager* histMan, TString histClasses);
 constexpr static uint32_t gkEventFillMap = VarManager::ObjTypes::ReducedEvent | VarManager::ObjTypes::ReducedEventExtended;
 constexpr static uint32_t gkMCEventFillMap = VarManager::ObjTypes::ReducedEventMC;
 constexpr static uint32_t gkTrackFillMap = VarManager::ObjTypes::ReducedTrack | VarManager::ObjTypes::ReducedTrackBarrel | VarManager::ObjTypes::ReducedTrackBarrelPID;
-constexpr static uint32_t gkTrackFillMapWithCov = VarManager::ObjTypes::ReducedTrack | VarManager::ObjTypes::ReducedTrackBarrel | VarManager::ObjTypes::ReducedTrackBarrelCov | VarManager::ObjTypes::ReducedTrackBarrelPID;
 constexpr static uint32_t gkParticleMCFillMap = VarManager::ObjTypes::ParticleMC;
 
+/// This is used to avoid having toplevel global variables which might appear as undefined.
+/// FIXME: it's probably a good idea to move also the others.
+struct FillMaps {
+  constexpr static uint32_t gkTrackWithCov = VarManager::ObjTypes::ReducedTrack | VarManager::ObjTypes::ReducedTrackBarrel | VarManager::ObjTypes::ReducedTrackBarrelCov | VarManager::ObjTypes::ReducedTrackBarrelPID;
+};
+
 struct DQEventSelection {
   Produces<aod::EventCuts> eventSel;
   OutputObj<THashList> fOutputList{"output"};