src/Pure/Tools/build.scala

     verbose: Boolean = false,
     export_files: Boolean = false): Results =
   {
     val build_options =
       options +
-        "ML_statistics" +
         "completion_limit=0" +
         "editor_tracing_messages=0" +
         "pide_reports=false"
 
     val store = Sessions.store(build_options)