torture: Make kvm.sh return failure upon build failure

The kvm.sh script uses kvm-find-errors.sh to evaluate whether or not
a build failed.  Unfortunately, kvm-find-errors.sh returns success if
there are no failed runs (including when there are no runs at all) even if
there are build failures.  This commit therefore makes kvm-find-errors.sh
return failure in response to build failures.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/kvm-find-errors.sh

@@ -39,6 +39,7 @@ done
 if test -n "$files"
 then
 	$editor $files
+	editorret=1
 else
 	echo No build errors.
 fi
@@ -62,5 +63,10 @@ then
 	exit 1
 else
 	echo No errors in console logs.
-	exit 0
+	if test -n "$editorret"
+	then
+		exit $editorret
+	else
+		exit 0
+	fi
 fi