kbuild: append -dirty for updated but uncommited changes

Compare the working copy with the last commit, instead of the index.
Signed-off-by: NUwe Zeisberger <zeisberg@informatik.uni-freiburg.de>
Acked-by: NRyan Anderson <ryan@michonline.com>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

scripts/setlocalversion

@@ -16,7 +16,7 @@ if head=`git rev-parse --verify HEAD 2>/dev/null`; then
 	fi
 
 	# Are there uncommitted changes?
-	if git diff-files | read dummy; then
+	if git diff-index HEAD | read dummy; then
 		printf '%s' -dirty
 	fi
 fi