Rather than repeatedly calling mc_from_tid() do this in the parent,
removing around a million function calls. Takes time spent in this
function from 40s to 36s.
(Bitbake rev: 28b3f0d8867804799420689c314ac4a8f01efb8c)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>