Currently the UI shows X is building, possibly multiple times but doesn't
say which of the multilibs that might be. This adds a prefix to the task
name so the mulitconfig being built can be identified.
(Bitbake rev: dfb775c67a96a79f3b85104870c0ade46ef2a9ea)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>