xcode_settings entries with list values override entries with the same key

pylib/gyp/xcodeproj_file.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.
 
 """Xcode project file generator.
 
 This module is both an Xcode project file generator and a documentation of the
 Xcode project file format.  Knowledge of the project file format was gained
 based on extensive experience with Xcode, and by making changes to projects in
 Xcode.app and observing the resultant changes in the associated project files.
@@ skipping 1538 matching lines @@
     'name':                       [0, str,  0, 1],
   })
 
   def HasBuildSetting(self, key):
     return key in self._properties['buildSettings']
 
   def GetBuildSetting(self, key):
     return self._properties['buildSettings'][key]
 
   def SetBuildSetting(self, key, value):
-    # TODO(mark): If a list, copy?
-    self._properties['buildSettings'][key] = value
+    if hasattr(value, '__iter__'):
+      self._properties['buildSettings'].setdefault(key, []).extend(value)
+    else:
+      self._properties['buildSettings'][key] = value
 
   def AppendBuildSetting(self, key, value):
-    if not key in self._properties['buildSettings']:
-      self._properties['buildSettings'][key] = []
-    self._properties['buildSettings'][key].append(value)
+    self._properties['buildSettings'].setdefault(key, []).append(value)
 
   def DelBuildSetting(self, key):
     if key in self._properties['buildSettings']:
       del self._properties['buildSettings'][key]
 
   def SetBaseConfiguration(self, value):
     self._properties['baseConfigurationReference'] = value
 
 class XCConfigurationList(XCObject):
   # _configs is the default list of configurations.
@@ skipping 1284 matching lines @@
       self._XCPrint(file, 0, '/* Begin ' + class_name + ' section */\n')
       for object in sorted(objects_by_class[class_name],
                            cmp=lambda x, y: cmp(x.id, y.id)):
         object.Print(file)
       self._XCPrint(file, 0, '/* End ' + class_name + ' section */\n')
 
     if self._should_print_single_line:
       self._XCPrint(file, 0, '}; ')
     else:
       self._XCPrint(file, 1, '};\n')