EvtPool: Make stat file non-empty to enable MonaLisa upload

(cherry picked from commit 1cb9267)

Author: sawenzel

MC/bin/o2dpg_sim_workflow.py

@@ -1593,7 +1593,7 @@ def addQCPerTF(taskName, needs, readerCommand, configFilePath, objectsFile=''):
    POOL_merge_task = createTask(name='poolmerge', needs=wfneeds, lab=["POOL"], mem='2000', cpu='1')
    POOL_merge_task['cmd'] = '${O2DPG_ROOT}/UTILS/root_merger.py -o evtpool.root -i ' + ','.join(tfpool)
    # also create the stat file with the event count
-   POOL_merge_task['cmd'] += '; RC=$?; root -l -q -b -e "auto f=TFile::Open(\\\"evtpool.root\\\"); auto t=(TTree*)f->Get(\\\"o2sim\\\"); int n=t->GetEntries(); std::ofstream((\\\"0_0_0_\\\"+std::to_string(n)+\\\".stat\\\").c_str()).close();" ; [[ ${RC} == 0 ]]'
+   POOL_merge_task['cmd'] += '; RC=$?; root -l -q -b -e "auto f=TFile::Open(\\\"evtpool.root\\\"); auto t=(TTree*)f->Get(\\\"o2sim\\\"); int n=t->GetEntries(); std::ofstream((\\\"0_0_0_\\\"+std::to_string(n)+\\\".stat\\\").c_str()) << \\\"# MonaLisa stat file for event pools\\\";" ; [[ ${RC} == 0 ]]'
    workflow['stages'].append(POOL_merge_task)
 
 # adjust for alternate (RECO) software environments