QtGStreamer doesn't link against needed libs when cross-building for Windows

[Nikos Chantziaras]

I'm using MXE (a mingw cross-compiler) to build various libraries for 
Windows under Linux.  Qt and GStreamer itself, and all their needed 
deps, build fine.  QtGStreamer however fails horribly.  It seems it 
doesn't link against the libraries it needs and the result is a 
humongous amount of "undefined reference" linker errors:

   http://pastebin.com/raw.php?i=NYGBrcdE

I'm building with:

   cmake .. \
         -DCMAKE_TOOLCHAIN_FILE='$(CMAKE_TOOLCHAIN_FILE)' \
         -DQTGSTREAMER_STATIC=ON \
         -DQTGSTREAMER_EXAMPLES=OFF \
         -DQTGSTREAMER_TESTS=OFF

What can I do to get a correct link step?