Introduce new ROOFIT_ATLAS_BENCHMARKS flag for conditional build

Author: guitargeek

root/roofit/CMakeLists.txt

@@ -1,6 +1,8 @@
-# Can only be enabled is you have the ATLAS RooFit extensions installed and you
-# set unlimited stack size with `ulimit -S -s unlimited`:
-#   add_subdirectory(atlas-benchmarks)
+if(ROOFIT_ATLAS_BENCHMARKS)
+  # Can only be enabled is you have the ATLAS RooFit extensions installed and you
+  # set unlimited stack size with `ulimit -S -s unlimited`:
+  add_subdirectory(atlas-benchmarks)
+endif()
 
 add_subdirectory(histfactory)
 add_subdirectory(roofit)