Tweak windows configuration file to include debug information in release builds.

gyp/configurations_msvs.gypi

 # Copyright (c) 2011, 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.
 
 {
   'target_defaults': {
     'configurations': {
       'Dart_Debug': {
         'msvs_settings': {
           'VCCLCompilerTool': {
@@ skipping 19 matching lines @@
             'InlineFunctionExpansion': '2',
             'EnableIntrinsicFunctions': 'true',
             'FavorSizeOrSpeed': '0',
             'ExceptionHandling': '0',
             'RuntimeTypeInfo': 'false',
             'OmitFramePointers': 'true',
             'StringPooling': 'true',
           },
           'VCLinkerTool': {
             'LinkIncremental': '1',
+            'GenerateDebugInformation': 'true',
             'OptimizeReferences': '2',
             'EnableCOMDATFolding': '2',
             'StackReserveSize': '2097152',
           },
         },
       },
     },
   },
 }