gRPC migration update

Change-Id: Icdd1a824948fa994cd36bd121c962f5ecf74e3cf
diff --git a/vendor/golang.org/x/sys/windows/empty.s b/vendor/golang.org/x/sys/windows/empty.s
new file mode 100644
index 0000000..fdbbbcd
--- /dev/null
+++ b/vendor/golang.org/x/sys/windows/empty.s
@@ -0,0 +1,9 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.12
+// +build !go1.12
+
+// This file is here to allow bodyless functions with go:linkname for Go 1.11
+// and earlier (see https://golang.org/issue/23311).