Fix addlicense on gflags BUILD

Author: Trinkle23897

third_party/gflags/BUILD

@@ -1 +1,15 @@
+## Copyright 2026 Garena Online Private Limited
+##
+## Licensed under the Apache License, Version 2.0 (the "License");
+## you may not use this file except in compliance with the License.
+## You may obtain a copy of the License at
+##
+##     http://www.apache.org/licenses/LICENSE-2.0
+##
+## Unless required by applicable law or agreed to in writing, software
+## distributed under the License is distributed on an "AS IS" BASIS,
+## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+## See the License for the specific language governing permissions and
+## limitations under the License.
+
 exports_files(["rules_cc_defs.patch"])