patch from chinmaygarde@ to make progress on mac, ios.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 9120e66e9d9ad6023ad37cf7670d7d95fef382b2..ac5dd23232743d8e6a9d5cc8944fa873946c1b97 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -270,9 +270,12 @@ config("compiler") {
         "i386",
       ]
     } else if (current_cpu == "arm") {
+      # TODO(GYP): we may need to distinguish between "arm64", "armv7",
+      # and "armv7s" for iOS, and hence need multiple current_cpu values
+      # rather than just "arm".
       common_mac_flags += [
         "-arch",
-        "armv7",
+        "arm64",
       ]
     }