Add apache2 SPDX headers to all source files (#48)

scripts/check-build-status.js

@@ -1,3 +1,9 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 /* eslint-disable no-undef */
 import fs from 'fs';
 import path from 'path';