Set an exit code when exiting build_sdk_summary in error.

pkg/analyzer/tool/summary/build_sdk_summary.dart

 import 'dart:io';
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/summarize_elements.dart';
 
 main(List<String> args) {
   if (args.length < 1 || args.length > 2) {
     _printUsage();
-    return;
+    exit(1);

[kevmoo, 2016/02/03 19:22:07]

consider setting exitCode = 1 and return.

exit(n) borks Observatory – so you can't do code coverage, etc.

[Paul Berry, 2016/02/04 13:27:34]

Done.

   }
   //
   // Prepare output file path.
   //
   String outputFilePath = args[0];
   if (FileSystemEntity.isDirectorySync(outputFilePath)) {
     print("'$outputFilePath' is a directory.");
     _printUsage();
-    return;
+    exit(1);
   }
   //
   // Prepare SDK path.
   //
   String sdkPath;
   if (args.length == 2) {
     sdkPath = args[1];
     if (!FileSystemEntity.isDirectorySync('$sdkPath/lib')) {
       print("'$sdkPath/lib' does not exist.");
       _printUsage();
-      return;
+      exit(1);
     }
   } else {
     sdkPath = DirectoryBasedDartSdk.defaultSdkDirectory.getAbsolutePath();
   }
   //
   // Prepare SDK.
   //
   DirectoryBasedDartSdk sdk = new DirectoryBasedDartSdk(new JavaFile(sdkPath));
   AnalysisContext context = sdk.context;
   //
@@ skipping 32 matching lines @@
  * The name of the SDK summary builder application.
  */
 const BINARY_NAME = "build_sdk_summary";
 
 /**
  * Print information about how to use the SDK summary builder.
  */
 void _printUsage() {
   print('Usage: $BINARY_NAME output_file_path [sdk_path]');
 }