Introduce build configuration to summary building.

pkg/analyzer/tool/summary/build_sdk_summaries.dart

 import 'dart:io';
 
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:analyzer/src/summary/flat_buffers.dart' as fb;
 import 'package:analyzer/src/summary/summary_file_builder.dart';
 
 main(List<String> args) {
   if (args.length < 1) {
     _printUsage();
     exitCode = 1;
@@ skipping 95 matching lines @@
   //
   BuilderOutput spec = includeSpec ? _buildOutput(sdkPath, false) : null;
   BuilderOutput strong = _buildOutput(sdkPath, true);
   return new SummaryOutput(spec, strong);
 }
 
 BuilderOutput _buildOutput(String sdkPath, bool strongMode) {
   String modeName = strongMode ? 'strong' : 'spec';
   print('Generating $modeName mode summary and index.');
   Stopwatch sw = new Stopwatch()..start();
-  BuilderOutput output = new SummaryBuilder.forSdk(sdkPath, strongMode).build();
+  SummaryBuildConfig config = new SummaryBuildConfig(strongMode: strongMode);
+  BuilderOutput output = new SummaryBuilder.forSdk(sdkPath, config).build();
   print('\tDone in ${sw.elapsedMilliseconds} ms.');
   return output;
 }
 
 /**
  * Open the flat buffer in [inputPath] and extract the byte array in the [field]
  * into the [outputPath] file.
  */
 void _extractSingleOutput(String inputPath, int field, String outputPath) {
   List<int> bytes = new File(inputPath).readAsBytesSync();
@@ skipping 19 matching lines @@
   print('    Generate a single file with summary and index.');
   print('  extract-spec-sum input_file output_file');
   print('    Extract the spec-mode summary file.');
   print('  extract-strong-sum input_file output_file');
   print('    Extract the strong-mode summary file.');
   print('  extract-spec-index input_file output_file');
   print('    Extract the spec-mode index file.');
   print('  extract-strong-index input_file output_file');
   print('    Extract the strong-mode index file.');
 }