Based upon the list of difference starting points, we can use the siggen.find_siginfo()
function call and the difference printing code to provide a list of differences
between the current build target and whatever can be obtained from the sstate cache.
(Bitbake rev: 7a77861feb62750ef166d2d1e89ed1f444ca8dc7)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>