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