system/window.h is no longer available by default and is part of
libnativewindow, so add it to the shared libraries. It has to be conditional
because the library is only present in O and later.

Really, we should only be depending on vndk/window.h now, but that's only
in O and changing would be pretty invasive.

Signed-off-by: Rob Herring <robh@kernel.org>