format using buildifier

using `buildifier -r .`

Change-Id: I774bc5e7e238ee526077c20ea17e76a52fa94391
diff --git a/tools/BUILD b/tools/BUILD
index 1fa2160..cc10083 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -1 +1 @@
-# Empty file - bazel treat directories with BUILD file as a package
\ No newline at end of file
+# Empty file - bazel treat directories with BUILD file as a package