Set optional LastSwiftUpdateCheck to Xcode project attributes.

pylib/gyp/generator/xcode.py

 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import filecmp
 import gyp.common
 import gyp.xcodeproj_file
 import gyp.xcode_ninja
 import errno
 import os
@@ skipping 604 matching lines @@
     pbxp = xcp.project
 
     # Set project-level attributes from multiple options
     project_attributes = {};
     if parallel_builds:
       project_attributes['BuildIndependentTargetsInParallel'] = 'YES'
     if upgrade_check_project_version:
       project_attributes['LastUpgradeCheck'] = upgrade_check_project_version
       project_attributes['LastTestingUpgradeCheck'] = \
           upgrade_check_project_version
+      project_attributes['LastSwiftUpdateCheck'] = \
+          upgrade_check_project_version
     pbxp.SetProperty('attributes', project_attributes)
 
     if project_version:
       xcp.project_file.SetXcodeVersion(project_version)
 
     # Add gyp/gypi files to project
     if not generator_flags.get('standalone'):
       main_group = pbxp.GetProperty('mainGroup')
       build_group = gyp.xcodeproj_file.PBXGroup({'name': 'Build'})
       main_group.AppendChild(build_group)
@@ skipping 633 matching lines @@
 
   for build_file in build_files:
     xcode_projects[build_file].Finalize1(xcode_targets, serialize_all_tests)
 
   for build_file in build_files:
     xcode_projects[build_file].Finalize2(xcode_targets,
                                          xcode_target_to_target_dict)
 
   for build_file in build_files:
     xcode_projects[build_file].Write()