Implement arflags in the GN build.

build/toolchain/win/BUILD.gn

 # Copyright (c) 2013 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/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 
 # Should only be running on Windows.
@@ skipping 127 matching lines @@
       }
       command = "$python_path gyp-win-tool asm-wrapper $env $ml {{defines}} {{include_dirs}} {{asmflags}} /c /Fo{{output}} {{source}}"
       description = "ASM {{output}}"
       outputs = [
         "$object_subdir/{{source_name_part}}.obj",
       ]
     }
 
     tool("alink") {
       rspfile = "{{output}}.rsp"
-      command = "$python_path gyp-win-tool link-wrapper $env False $lib /nologo /ignore:4221 /OUT:{{output}} @$rspfile"
+      command = "$python_path gyp-win-tool link-wrapper $env False $lib /nologo {{arflags}} /OUT:{{output}} @$rspfile"
       description = "LIB {{output}}"
       outputs = [
         # Ignore {{output_extension}} and always use .lib, there's no reason to
         # allow targets to override this extension on Windows.
         "{{output_dir}}/{{target_output_name}}.lib",
       ]
       default_output_extension = ".lib"
       default_output_dir = "{{target_out_dir}}"
 
       # The use of inputs_newline is to work around a fixed per-line buffer
@@ skipping 217 matching lines @@
 
   msvc_toolchain("winrt_x64") {
     environment = "environment.winrt_x64"
     cl = "${goma_prefix}\"${vc_bin_dir}/cl.exe\""
     is_clang = false
 
     toolchain_cpu = "x64"
     toolchain_os = current_os
   }
 }