Add missing copyright header.

PiperOrigin-RevId: 858095311

Author: gonnet

BUILD.bazel

@@ -1,3 +1,12 @@
+# Copyright (c) 2017 Facebook Inc.
+# Copyright (c) 2015-2017 Georgia Institute of Technology
+# All rights reserved.
+#
+# Copyright 2019-2026 Google LLC
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
 load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library", "cc_test")
 
 licenses(["notice"])