Revert of clang/win: Stop passing -Qunused-arguments.

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 15 matching lines @@
       # can also produce a table of the image's safe exception handlers. This
       # table specifies for the operating system which exception handlers are
       # valid for the image. Note that /SAFESEH isn't accepted on the command
       # line, only /safeseh. This is only accepted by ml.exe, not ml64.exe.
       "/safeseh",
     ]
   }
 
   cflags = [
     "/Gy",  # Enable function-level linking.
+    "/GS",  # Enable buffer security checking.
     "/FS",  # Preserve previous PDB behavior.
     "/bigobj",  # Some of our files are bigger than the regular limits.
 
     # Tell the compiler to crash on failures. This is undocumented
     # and unsupported but very handy.
     "/d2FastFail",
   ]
-  if (!is_clang) {
-    # TODO(thakis): Enable this with clang too, https://crbug.com/598767
-    cflags += [ "/GS" ]  # Enable buffer security checking.
-  }
 
   # Force C/C++ mode for the given GN detected file type. This is necessary
   # for precompiled headers where the same source file is compiled in both
   # modes.
   cflags_c = [ "/TC" ]
   cflags_cc = [ "/TP" ]
 
   if (visual_studio_version == "2015") {
     cflags += [
       # Work around crbug.com/526851, bug in VS 2015 RTM compiler.
@@ skipping 324 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" ]
   }
 }