Build the proto go bindings generator plugin.

Change-Id: I3e043c58abe9b52da1a63c54947f4992827e2832
diff --git a/protoc-gen-go/BUILD.gn b/protoc-gen-go/BUILD.gn
new file mode 100644
index 0000000..4734353
--- /dev/null
+++ b/protoc-gen-go/BUILD.gn
@@ -0,0 +1,21 @@
+# Copyright 2017 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/go/go_binary.gni")
+import("//build/host.gni")
+
+assert(current_toolchain == host_toolchain)
+
+go_binary("protoc-gen-go") {
+  gopackage = "protoc-gen-go"
+}
+
+install_host_tools("host") {
+  deps = [
+    ":protoc-gen-go",
+  ]
+  outputs = [
+    "protoc-gen-go",
+  ]
+}