Fix Windows linker warning in components/policy/generated.lib

components/policy/BUILD.gn

 # Copyright 2014 The Chromium 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/config/chrome_build.gni")
 import("//build/config/features.gni")
 import("//components/policy/resources/policy_templates.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("//tools/grit/grit_rule.gni")
 
@@ skipping 148 matching lines @@
   }
 
   static_library("generated") {
     sources = [
       constants_header_path,
       constants_source_path,
       protobuf_decoder_path,
       risk_tag_header_path,
     ]
 
+    defines = [ "POLICY_COMPONENT_IMPLEMENTATION" ]
     public_deps = [
       ":cloud_policy_code_generate",
       ":cloud_policy_proto_generated_compile",
       "//base",
       "//third_party/protobuf:protobuf_lite",
     ]
   }
 
   if (is_android) {
     import("//build/config/android/rules.gni")
@@ skipping 127 matching lines @@
                "--grit_info",
                rebase_path(grit_info_script, root_build_dir),
              ] + grit_defines
       deps = [
         ":add_version",
         ":policy_templates",
       ]
     }
   }
 }