Fix: test_seek static linking

./configure --disable-shared --enable-static
make
make check

The make check fails for test_seek.

Fix this by ensuring that test_seek has a dependency on libbabeltrace
and libbabeltrace-ctf. This is a temporary work-around until we improve
our plugin handling.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>