GN: Fix iOS error in audio_device and rtc_base

webrtc/base/BUILD.gn

 # Copyright (c) 2014 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.
 
 import("//build/config/crypto.gni")
 import("//build/config/ui.gni")
 import("../build/webrtc.gni")
 
+# Enable OpenSSL (BoringSSL) for iOS. This is covered in webrtc/supplement.gypi

[kjellander_webrtc, 2015/11/23 09:18:36]

This is globally applied for GYP with supplement.gypi but here it's kept much
closer to where it's used, which is by design in GN (and is great).

And if I try to put this into any of the common configs of
https://chromium.googlesource.com/external/webrtc/+/master/webrtc/BUILD.gn I get
this when running gn gen:
ERROR at //webrtc/BUILD.gn:95:21: Assignment had no effect.
      use_openssl = true
                    ^---
You set the variable "use_openssl" here and it was unused before it went
out of scope.

+# for the GYP build.
+import("//build_overrides/webrtc.gni")
+if (is_ios && !build_with_chromium) {
+  use_openssl = true
+}
+
 config("rtc_base_config") {
   include_dirs = [
     "//third_party/jsoncpp/overrides/include",
     "//third_party/jsoncpp/source/include",
   ]
 
   defines = [
     "FEATURE_ENABLE_SSL",
     "LOGGING=1",
   ]
@@ skipping 563 matching lines @@
       "linux.cc",
       "linux.h",
     ]
   }
 
   if (is_nacl) {
     deps += [ "//native_client_sdk/src/libraries/nacl_io" ]
     defines += [ "timezone=_timezone" ]
   }
 }