Merge branch 'stable-3.1'

* stable-3.1:
  Add an empty tools/BUILD file explicitly for Bazel

Change-Id: I26438c074731cddcc09228931beff403437da229
diff --git a/tools/BUILD b/tools/BUILD
new file mode 100644
index 0000000..1fa2160
--- /dev/null
+++ b/tools/BUILD
@@ -0,0 +1 @@
+# Empty file - bazel treat directories with BUILD file as a package
\ No newline at end of file