This commit adds -T path/to/linker_script to the output
of "compel ldflags", so compel user does not have to specify
one manually.

This commit also makes use of this functionality in criu/pie
and compel/test.

NOTE this commit also drops the linker script dependency
in criu/pie/Makefile, meaning if it will be changed that
won't cause a rebuild. I hope it's not a big issue, and it is
sort of inevitable as compel is becoming a separate tool.

travis-ci: success for More polishing for compel cli
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>