Implement arflags in the GN build.

build/config/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/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 
 assert(is_win)
 
@@ skipping 85 matching lines @@
 
     # Clang runtime libraries, such as the sanitizer runtimes, live here.
     lib_dirs = [ "//third_party/llvm-build/Release+Asserts/lib/clang/3.9.0/lib/windows" ]
   }
 
   if (is_syzyasan) {
     # SyzyAsan needs /PROFILE turned on to produce appropriate pdbs.
     assert(!is_win_fastlink, "/PROFILE and /DEBUG:FASTLINK are incompatible")
     ldflags = [ "/PROFILE" ]
   }
+
+  # arflags apply only to static_libraries. The normal linker configs are only
+  # set for executable and shared library targets so arflags must be set
+  # elsewhere. Since this is relatively contained, we just apply them in this
+  # more general config and they will only have an effect on static libraries.
+  arflags = [
+    # "No public symbols found; archive member will be inaccessible." This
+    # means that one or more object files in the library can never be
+    # pulled in to targets that link to this library. It's just a warning that
+    # the source file is a no-op.
+    "/ignore:4221",
+  ]
 }
 
 config("vs_code_analysis") {
   if (use_vs_code_analysis) {
     # When use_vs_code_analysis is specified add the /analyze switch to enable
     # static analysis. Specifying /analyze:WX- says that /analyze warnings
     # should not be treated as errors.
     cflags = [ "/analyze:WX-" ]
 
     # Also, disable various noisy warnings that have low value.
@@ skipping 271 matching lines @@
 
 # Internal stuff --------------------------------------------------------------
 
 # Config used by the MIDL template to disable warnings.
 config("midl_warnings") {
   if (is_clang) {
     # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
     cflags = [ "-Wno-extra-tokens" ]
   }
 }