Analyzer should set exitCode instead of calling exit

pkg/analyzer/bin/analyzer.dart

 #!/usr/bin/env dart
 
 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /** The entry point for the analyzer. */
 library analyzer;
 
 import 'dart:async';
@@ skipping 34 matching lines @@
       print("errors:$errorsTime");
       print("hints:$hintsTime");
       print("angular:$angularTime");
       print("other:${totalTime
         - (scanTime + parseTime + resolveTime + errorsTime + hintsTime
            + angularTime)}}");
       print("total:$totalTime");
       print("");
       print("Time spent in instanceof = ${instanceOfTimer.elapsedMilliseconds}");
     }
-
-    exit(result.ordinal);
+    exitCode = result.ordinal;
   }
 }
 
 ErrorSeverity _runAnalyzer(CommandLineOptions options) {
   if (!options.machineFormat) {
     stdout.writeln("Analyzing ${options.sourceFiles}...");
   }
   ErrorSeverity allResult = ErrorSeverity.NONE;
   String sourcePath = options.sourceFiles[0];
   sourcePath = sourcePath.trim();
@@ skipping 74 matching lines @@
         stdout.writeln('>>> TEST $resultPassString ${stopwatch.elapsedMilliseconds}ms');
       } catch (e, stackTrace) {
         stderr.writeln(e);
         stderr.writeln(stackTrace);
         stderr.writeln('>>> EOF STDERR');
         stdout.writeln('>>> TEST CRASH');
       }
     });
   }
 }