qt5.qtbase: add cf-private on darwin

    Undefined symbols for architecture x86_64:
      "_OBJC_CLASS_$_NSDate", referenced from:
          objc-class-ref in qcore_foundation.o
      "_OBJC_CLASS_$_NSURL", referenced from:
          objc-class-ref in qcore_foundation.o
      "_OBJC_CLASS_$_NSData", referenced from:
          objc-class-ref in qcore_foundation.o
      "_CFURLCopyResourcePropertyForKey", referenced from:
          hasResourcePropertyFlag(QFileSystemMetaData const&, QFileSystemEntry const&, __CFString const*) in qfilesystemengine_unix.o
      "_CFURLCreateBookmarkDataFromFile", referenced from:
          QFileSystemEngine::getLinkTarget(QFileSystemEntry const&, QFileSystemMetaData&) in qfilesystemengine_unix.o
      "_kCFURLIsAliasFileKey", referenced from:
          QFileSystemEngine::fillMetaData(QFileSystemEntry const&, QFileSystemMetaData&, QFlags<QFileSystemMetaData::MetaDataFlag>) in qfilesystemengine_unix.o
      "_kCFURLIsHiddenKey", referenced from:
          QFileSystemEngine::fillMetaData(QFileSystemEntry const&, QFileSystemMetaData&, QFlags<QFileSystemMetaData::MetaDataFlag>) in qfilesystemengine_unix.o
      "_kCFURLIsPackageKey", referenced from:
          QFileSystemEngine::fillMetaData(QFileSystemEntry const&, QFileSystemMetaData&, QFlags<QFileSystemMetaData::MetaDataFlag>) in qfilesystemengine_unix.o
      "_CFURLCreateByResolvingBookmarkData", referenced from:
          QFileSystemEngine::getLinkTarget(QFileSystemEntry const&, QFileSystemMetaData&) in qfilesystemengine_unix.o
    ld: symbol(s) not found for architecture x86_64