Fix transitions for image_download and activation

Change-Id: I713ada52eef9d275c7d7596026e178c7382e8335
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..69309e4
--- /dev/null
+++ b/vendor/golang.org/x/sys/windows/empty.s
@@ -0,0 +1,8 @@
+// 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.
+
+// +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).