GN: Enable ARC for Mac and iOS in rtc_* templates

webrtc/sdk/BUILD.gn

Index: webrtc/sdk/BUILD.gn
diff --git a/webrtc/sdk/BUILD.gn b/webrtc/sdk/BUILD.gn
index 5e89d54cfb3aa7b2702dd478e92e03970456a819..6a238b2978b3f9c06ff0138eb5f9cbfd5a4082d3 100644
--- a/webrtc/sdk/BUILD.gn
+++ b/webrtc/sdk/BUILD.gn
@@ -31,10 +31,7 @@ if (is_ios || is_mac) {
     deps = [
       "../base:rtc_base",
     ]
-    configs += [
-      "..:common_objc",
-      "//build/config/compiler:enable_arc",
-    ]
+    configs += [ "..:common_objc" ]
     public_configs = [ ":rtc_sdk_common_objc_config" ]
     sources = [
       "objc/Framework/Classes/NSString+StdString.h",
@@ -223,10 +220,7 @@ if (is_ios || is_mac) {
       ]
     }
 
-    configs += [
-      "..:common_objc",
-      "//build/config/compiler:enable_arc",
-    ]
+    configs += [ "..:common_objc" ]
 
     public_configs = [ ":rtc_sdk_common_objc_config" ]
 
@@ -365,10 +359,7 @@ if (is_ios || is_mac) {
         "VideoToolbox.framework",
       ]
 
-      configs += [
-        "..:common_objc",
-        "//build/config/compiler:enable_arc",
-      ]
+      configs += [ "..:common_objc" ]
 
       public_configs = [ ":rtc_sdk_common_objc_config" ]
 
@@ -398,10 +389,7 @@ if (is_ios || is_mac) {
       "objc/Framework/Classes/h264_video_toolbox_nalu.h",
     ]
 
-    configs += [
-      "//webrtc:common_objc",
-      "//build/config/compiler:enable_arc",
-    ]
+    configs += [ "//webrtc:common_objc" ]
 
     deps = [
       ":rtc_sdk_common_objc",