as-needed.inc: add babeltrace exception

as-needed.inc: add babeltrace exception

The babeltrace command has plugins which it specifies in its link step
but on which (in the linker's view) it does not depend, so --as-needed
causes some of them to be omitted from the executable's dependencies.
This prevents babeltrace on OE-built systems from handling
streaming/live tracing sessions.

Babeltrace's makefiles already try to prevent this by using
--no-as-needed, but --as-needed gets placed afterward in the command
line, so it wins.

Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(From OE-Core master rev: d3fc696bf1c0c5e9a0d238fb86e58771cfbe9cae)
Signed-off-by: Joshua Lock <joshua.g.lock@intel.com>