classes/sanity: send sanity check failure as a separate event for Hob
In order to show a friendlier error message within Hob that does not
bury the actual sanity error in our typical preamble about disabling
sanity checks, use a separate event to indicate that sanity checks
failed.
This change is intended to work together with the related change to
BitBake, however it has a check to ensure that it does not fail with
older versions that do not include that change.
Fixes [YOCTO #2336].
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
