code: @Exported
      @QuickSilver
      public RunT getFirstBuild() {
          SortedMap<Integer, ? extends RunT> runs = _getRuns();
  
          if (runs.isEmpty())
              return null;
          return runs.get(runs.lastKey());
      }
docs: Returns the oldest build in the record.
  @see LazyBuildMixIn#getFirstBuild