Some build environments check out source code as readonly. When it is copied into the scratch dir for the test-cache test, the files are copied as readonly, and appending to README.md in the scratch directory fails. So first make the file writable before appending to it.
Some build environments check out source code as readonly. When it is copied into the scratch dir for the test-cache test, the files are copied as readonly, and appending to README.md in the scratch directory fails. So first make the file writable before appending to it.