Fix the dirty repository check to detect any changes, including
untracked files and uncommitted changes in the index.
(From OE-Core rev: f03fa8bbafa82ce6b09c08bf86011b6c51eb3531)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>