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: d93ddd185dde53f50aea06ada094bb0d9b5ba4f0)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>