File to which metrics are dumped per compilation.
A CSV format is used if the file ends with .csv otherwise a more
human readable format is used. The fields in the CSV format are:
           compilable - method being compiled
  compilable_identity - identity hash code of compilable
       compilation_nr - where this compilation lies in the ordered
                        sequence of all compilations identified by
                        compilable_identity
       compilation_id - runtime issued identifier for the compilation
          metric_name - name of metric
         metric_value - value of metric
