xcode-ninja should copy the product extension to the wrapper project to avoid possible name clashes

[GoogleCodeExporter]

Steps to reproduce:
1. Copy the folder test/mac/loadable-module-bundle-product-extension to a temp 
location, e.g.
    cp -R test/mac/loadable-module-bundle-product-extension/ /tmp/bug && cd /tmp/bug
2. Run
    gyp -f xcode-ninja -G xcode_ninja_target_pattern="^.*$" --depth=. test.gyp

Expected Results:
No error

Actual Results:
gyp fails with the following error:
Traceback (most recent call last):
  File "gyp_main.py", line 18, in <module>
    sys.exit(gyp.script_main())
  File "pylib/gyp/__init__.py", line 544, in script_main
    return main(sys.argv[1:])
  File "pylib/gyp/__init__.py", line 537, in main
    return gyp_main(args)
  File "pylib/gyp/__init__.py", line 522, in gyp_main
    generator.GenerateOutput(flat_list, targets, data, params)
  File "pylib/gyp/generator/xcode.py", line 705, in GenerateOutput
    force_extension=spec.get('product_extension'))
  File "pylib/gyp/xcodeproj_file.py", line 2369, in __init__
    products_group.AppendChild(file_ref)
  File "pylib/gyp/xcodeproj_file.py", line 1163, in AppendChild
    self._AddChildToDicts(child)
  File "pylib/gyp/xcodeproj_file.py", line 1146, in _AddChildToDicts
    raise ValueError, 'Found multiple children with path ' + child_path
ValueError: Found multiple children with path 
$(BUILT_PRODUCTS_DIR)/Collide.bundle

Original issue reported on code.google.com by tobias.h...@ableton.com on 28 Aug 2014 at 2:44