For some recipes, such as those that inherit cargo-update-recipe-crates,
we need to run additional tasks once the new sources have been unpacked.
Introduce a new variable RECIPE_UPDATE_EXTRA_TASKS which is a space-
delimited list of tasks to run after the new sources have been
unpacked in scripts/lib/devtool/upgrade.py ugrade() method.
Signed-off-by: Tim Orling <tim.orling@konsulko.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>