Turn //mojo/public/cpp/bindings and //mojo/public/cpp/system into components

mojo/public/cpp/bindings/BUILD.gn

Index: mojo/public/cpp/bindings/BUILD.gn
diff --git a/mojo/public/cpp/bindings/BUILD.gn b/mojo/public/cpp/bindings/BUILD.gn
index 9b9135003603a960fd35eff596cd0a632e74cd91..66a3729c96205b01c766d7c44cc7cb905d20703f 100644
--- a/mojo/public/cpp/bindings/BUILD.gn
+++ b/mojo/public/cpp/bindings/BUILD.gn
@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-static_library("bindings") {
+component("bindings") {
   sources = [
     "array.h",
     "array_data_view.h",
@@ -19,6 +19,7 @@ static_library("bindings") {
     "associated_interface_request.h",
     "binding.h",
     "binding_set.h",
+    "bindings_export.h",
     "connection_error_callback.h",
     "connector.h",
     "enum_traits.h",
@@ -140,6 +141,8 @@ static_library("bindings") {
     "//base",
     "//mojo/public/interfaces/bindings:bindings_cpp_sources",
   ]
+
+  defines = [ "MOJO_CPP_BINDINGS_IMPLEMENTATION" ]
 }
 
 source_set("struct_traits") {