gyp incorrectly generates Xcode projects that use Base.lproj localization for xibs and storyboards.

What steps will reproduce the problem?

Given a gyp file with a target like:

    {
      'target_name': 'WatchApp',
      'product_name': 'WatchApp',
      'type': 'executable',
      'mac_bundle': 1,
      'ios_watch_app': 1,
      'mac_bundle_resources': [
        'WatchApp/Images.xcassets',
        'WatchApp/Base.lproj/Interface.storyboard',
        '<!@(find WatchApp/*.lproj -type f -name "InfoPlist.strings")',
        '<!@(find WatchApp/*.lproj -type f -name "Interface.strings")',
        '<!@(find WatchApp/*.lproj -type f -name "Localizable.strings")',
      ],
      'sources': [
        'WatchApp/AppInfo.plist',
      ],
      'xcode_settings': {
        'ASSETCATALOG_COMPILER_APPICON_NAME': 'AppIcon',
        'INFOPLIST_FILE': 'WatchApp/AppInfo.plist',
        'IPHONEOS_DEPLOYMENT_TARGET': '8.2',
        'SKIP_INSTALL': 'YES',
        'COPY_PHASE_STRIP': 'NO',
        'TARGETED_DEVICE_FAMILY': '4',
        'TARGETED_DEVICE_FAMILY[sdk=iphonesimulator*]': '1,4',
      },
    },

And input directories in the file system:
Base.lproj with: Interface.storyboard
en.lproj with: Interface.strings: Localizable.strings InfoPlist.strings
fr.lproj with: Interface.strings: Localizable.strings InfoPlist.strings

What is the expected output?

The generated Xcode project has Localizable.strings 

What do you see instead?

        EFD7D2B7F8E1A98C63486EAF /* Localizable.strings */ = {
            isa = PBXVariantGroup;
            children = (
                03D630A109123736EA8D2CA5 /* en */,
                BAD2A34301459C7B86E00DF1 /* fr */,
                       );

...
        FAD9A92EC0A79349966AABE7 /* Interface.storyboard */ = {
            isa = PBXVariantGroup;
            children = (
                60D8968FAA6DA94C05F54C79 /* Base */,
            );
            name = Interface.storyboard;
            sourceTree = "<group>";
        };

...

That is, gyp correctly generates each separate XX.lproj as a member of the 
'children' list of Localizable.strings, or InfoPlist.strings, but it fails to 
do it with .xib and .storyboard files.

This causes the built binary to not be correctly localized when run in one of 
the other languages that should be supported.

What version of the product are you using? On what operating system?

OS X 10.10.3

Please provide any additional information below.

Original issue reported on code.google.com by oster@google.com on 17 Apr 2015 at 9:11

CChenX / gyp

gyp incorrectly generates Xcode projects that use Base.lproj localization for xibs and storyboards. #489