Fix the license to match LICENSE

(Code was committed by Googler, so it is owned by Google. I can change it.)

BUILD.gn

@@ -1,16 +1,26 @@
-# Copyright 2020 Google Inc. All rights reserved.
+# Copyright (c) 2020 Google LLC
 #
-# 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
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and/or associated documentation files (the "Materials"),
+# to deal in the Materials without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Materials, and to permit persons to whom the
+# Materials are furnished to do so, subject to the following conditions:
 #
-#     http://www.apache.org/licenses/LICENSE-2.0
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Materials.
 #
-# 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.
+# MODIFICATIONS TO THIS FILE MAY MEAN IT NO LONGER ACCURATELY REFLECTS KHRONOS
+# STANDARDS. THE UNMODIFIED, NORMATIVE VERSIONS OF KHRONOS SPECIFICATIONS AND
+# HEADER INFORMATION ARE LOCATED AT https://www.khronos.org/registry/
+#
+# THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM,OUT OF OR IN CONNECTION WITH THE MATERIALS OR THE USE OR OTHER DEALINGS
+# IN THE MATERIALS.
 
 config("spv_headers_public_config") {
   include_dirs = [ "include" ]