Add a snapshot of flutter/engine/src/build to our sdk

build/toolchain/clang.gni

Index: build/toolchain/clang.gni
diff --git a/build/toolchain/clang.gni b/build/toolchain/clang.gni
new file mode 100644
index 0000000000000000000000000000000000000000..c6803844d8b22340f75ccba87851635ad9ddedc1
--- /dev/null
+++ b/build/toolchain/clang.gni
@@ -0,0 +1,9 @@
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+declare_args() {
+  # Enable the optional type profiler in Clang, which will tag heap allocations
+  # with the allocation type.
+  use_clang_type_profiler = false
+}