GN: Fix windows clang errors. Attempt 2.

webrtc/examples/BUILD.gn

 # Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 if (is_android) {
   import("//build/config/android/config.gni")
@@ skipping 373 matching lines @@
       # Gtk requires gmodule, but it does not list it as a dependency in some
       # misconfigured systems.
       packages = [
         "gmodule-2.0",
         "gtk+-2.0",
         "gthread-2.0",
       ]
     }
   }
 
+  config("peerconnection_client_warnings_config") {
+    if (is_win && is_clang) {
+      cflags = [
+        # Disable warnings failing when compiling with Clang on Windows.
+        # https://bugs.chromium.org/p/webrtc/issues/detail?id=5366
+        "-Wno-format",
+
+        # See https://bugs.chromium.org/p/webrtc/issues/detail?id=6271
+        # for -Wno-reorder and -Wno-sign-compare
+        "-Wno-reorder",
+        "-Wno-sign-compare",
+      ]
+    }
+  }
+
   executable("peerconnection_client") {
     sources = [
       "peerconnection/client/conductor.cc",
       "peerconnection/client/conductor.h",
       "peerconnection/client/defaults.cc",
       "peerconnection/client/defaults.h",
       "peerconnection/client/peer_connection_client.cc",
       "peerconnection/client/peer_connection_client.h",
     ]
     if (is_clang) {
       # Suppress warnings from the Chromium Clang plugin.
       # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
       configs -= [ "//build/config/clang:find_bad_constructs" ]
     }
     if (is_win) {
       sources += [
         "peerconnection/client/flagdefs.h",
         "peerconnection/client/main.cc",
         "peerconnection/client/main_wnd.cc",
         "peerconnection/client/main_wnd.h",
       ]
       cflags = [ "/wd4245" ]
       configs += [ "//build/config/win:windowed" ]
     }
-    if (is_win && is_clang) {
-      cflags = [
-        # Disable warnings failing when compiling with Clang on Windows.
-        # https://bugs.chromium.org/p/webrtc/issues/detail?id=5366
-        "-Wno-reorder",
-        "-Wno-unused-function",
-      ]
-    }
     if (is_linux) {
       sources += [
         "peerconnection/client/linux/main.cc",
         "peerconnection/client/linux/main_wnd.cc",
         "peerconnection/client/linux/main_wnd.h",
       ]
       libs = [
         "X11",
         "Xcomposite",
         "Xext",
         "Xrender",
       ]
       public_configs = [ ":gtk2_config" ]
     }
     deps = [
       "//build/config/sanitizers:deps",
       "//webrtc/api:libjingle_peerconnection",
       "//webrtc/system_wrappers:field_trial_default",
       "//webrtc/system_wrappers:metrics_default",
     ]
+    configs += [ ":peerconnection_client_warnings_config" ]
     if (rtc_build_json) {
       deps += [ "//third_party/jsoncpp" ]
     }
   }
   executable("peerconnection_server") {
     sources = [
       "peerconnection/server/data_socket.cc",
       "peerconnection/server/data_socket.h",
       "peerconnection/server/main.cc",
       "peerconnection/server/peer_channel.cc",
@@ skipping 58 matching lines @@
       "//webrtc/system_wrappers:field_trial_default",
       "//webrtc/system_wrappers:metrics_default",
     ]
     if (is_clang) {
       # Suppress warnings from the Chromium Clang plugin.
       # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
       configs -= [ "//build/config/clang:find_bad_constructs" ]
     }
   }
 }