[DF] Fix runtime errors in wmass benchmark

I.e. let cling find the headers it needs.

Author: eguiraud

root/tree/dataframe/wmass/CMakeLists.txt

@@ -3,6 +3,7 @@ if(rootbench-datafiles AND ROOT_root7_FOUND) # using ROOT_root7_FOUND as a proxy
 
    file(COPY RDFprocessor/ DESTINATION ${CMAKE_CURRENT_BINARY_DIR} FILES_MATCHING PATTERN "*.py")
    file(COPY python/ DESTINATION ${CMAKE_CURRENT_BINARY_DIR} FILES_MATCHING PATTERN "*.py")
+   file(COPY inc/ DESTINATION ${CMAKE_CURRENT_BINARY_DIR}/inc)
 
    add_library(SignalAnalysis SHARED
       src/TH3weightsHelper.cpp

root/tree/dataframe/wmass/runSignalAnalysis.py

@@ -19,6 +19,8 @@ def analysis(nthreads):
     else:
         ROOT.ROOT.DisableImplicitMT()
 
+    ROOT.gInterpreter.AddIncludePath('./')
+    ROOT.gInterpreter.Declare('#include "inc/classes.h"')
     ROOT.gSystem.Load('libSignalAnalysis.so')