Qt*Config.cmake doesn't provide INCLUDE_DIRS for private headers

With Qt-5.2.1 (or 5.3.0-alpha) Qt's cmake config files don't seem to be able to find private headers. Qt5GuiConfig.cmake looks like below, for example:

set(_Qt5Gui_OWN_INCLUDE_DIRS "${_qt5Gui_install_prefix}/include/qt5/" "${_qt5Gui_install_prefix}/include/qt5/QtGui")
    set(Qt5Gui_PRIVATE_INCLUDE_DIRS "")
    include("${CMAKE_CURRENT_LIST_DIR}/ExtraSourceIncludes.cmake" OPTIONAL)

The problem with that seems to be that there is no ExtraSourceIncludes.cmake installed anywhere, except as /usr/share/qt5/mkspecs/features/data/cmake/ExtraSourceIncludes.cmake.in

When I install Qt from the current stable branch I get the following file which finds the private headers (tested with KF5GuiAddons):

set(_Qt5Gui_OWN_INCLUDE_DIRS "${_qt5Gui_install_prefix}/include/qt5/" "${_qt5Gui_install_prefix}/include/qt5/QtGui")
    set(Qt5Gui_PRIVATE_INCLUDE_DIRS
        "${_qt5Gui_install_prefix}/include/qt5/QtGui/5.3.0"
        "${_qt5Gui_install_prefix}/include/qt5/QtGui/5.3.0/QtGui"
    )

I'm not sure how those files are generated so i have to ask is this bug or am I doing something wrong?