Empty overrides file for GN on Mac

build_overrides/build.gni

Index: build_overrides/build.gni
diff --git a/build_overrides/build.gni b/build_overrides/build.gni
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+# Copyright 2016 The LibYuv 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.
+
+# Using same overrides as WebRTC
+# See https://bugs.chromium.org/p/webrtc/issues/detail?id=5453.
+# Some WebRTC targets require the 10.7 deployment version of the Mac SDK and a
+# 10.11 min SDK but those targets are only used in non-Chromium builds. We can
+# remove this when Chromium drops 10.6 support and also requires 10.7.
+mac_sdk_min_build_override = "10.11"
+mac_deployment_target_build_override = "10.7"