fix failing bazel workspace relative path test

pkg/analyzer_cli/lib/src/options.dart

 // Copyright (c) 2015, 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.
 
 library analyzer_cli.src.options;
 
 import 'dart:io';
 
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/command_line/arguments.dart';
@@ skipping 232 matching lines @@
           options.packageConfigPath != null) {
         printAndFail("Cannot specify both '--package-root' and '--packages.");
         return null; // Only reachable in testing.
       }
     }
 
     // Build mode.
     if (options.buildModePersistentWorker && !options.buildMode) {
       printAndFail('The option --persisten_worker can be used only '
           'together with --build-mode.');
+      return null; // Only reachable in testing.
     }
     if (options.buildSummaryOnlyDiet && !options.buildSummaryOnly) {
       printAndFail('The option --build-summary-only-diet can be used only '
           'together with --build-summary-only.');
+      return null; // Only reachable in testing.
     }
 
     return options;
   }
 
   /// The source files to analyze
   List<String> get sourceFiles => _sourceFiles;
 
   /// Replace the sourceFiles parsed from the command line.
   void rewriteSourceFiles(List<String> newSourceFiles) {
@@ skipping 253 matching lines @@
         'Usage: $_binaryName [options...] <directory or list of files>');
     errorSink.writeln('');
     errorSink.writeln(parser.usage);
     errorSink.writeln('');
     errorSink.writeln('''
 Run "dartanalyzer -h -v" for verbose help output, including less commonly used options.
 For more information, see http://www.dartlang.org/tools/analyzer.
 ''');
   }
 }