When we're running with bitbake -b, BB_TASKDEPDATA is incorrect and limited.
We really need a way to know this from the metadata and this new variable
provides this in worker context. This means existing code can stop having
to guess.
(Bitbake rev: 05763bc886024dcce2ce6b3060fb00abf79a9402)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>