problem building with qtav

[Simon Frei]

I just started to build digikam with the new qtav integration. However
it does not find the include dirs (see boostrap output below). I
compiled qtav from source and create a .deb package for it (all
preconfigured by qtav devs). This installs the include dir to
/usr/include/x86_64-linux-gnu/qt5/QtAVWidgets (usual path on debian)
which is not found by the provided FindQtAv.cmake file. I added
    ${_qt5_install_prefix}/../../../include/x86_64-linux-gnu/qt5
to the HINTS and now it finds it. This is quite ugly, but seems necessary.

-- QtAV search path: /usr/lib/x86_64-linux-gnu/cmake
-- Could NOT find QtAV (missing:  QTAV_INCLUDE_DIRS)
-- QtAV_FOUND       = FALSE
-- QtAV_INCLUDE_DIR = QTAV_CORE_INCLUDE_DIR-NOTFOUND
QTAV_WIDGETS_INCLUDE_DIR-NOTFOUND
-- QtAV_LIBRARIES   =
/usr/lib/x86_64-linux-gnu/libQtAV.so;/usr/lib/x86_64-linux-gnu/libQtAVWidgets.so