make: pie -- Add generation of dep files

Otherwise pie may not be re-built if headers
are changed.

https://bugzilla.openvz.org/show_bug.cgi?id=2465



Reported-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>