code: @GwtIncompatible("Unnecessary")
    private boolean shouldGenerateMapPerModule(B options) {
      return options.sourceMapOutputPath != null
          && options.sourceMapOutputPath.contains("%outname%");
    }
docs: Returns true if and only if a source map file should be generated for each module, as opposed
  to one unified map. This is specified by having the source map pattern include the %outname%
  variable.