Fix: libbabeltrace lib build dependencies

The "no-as-needed" is only needed for plugins, not for libraries we
depend upon, so it is not really needed here. Using LIBADD instead
ensures that libbabeltrace gets rebuilt whenever the content of
libbabeltrace_types (statically linked) is modified.

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