GitHub Pages: Deprecating symlinks in non-Actions builds

To ensure the security of our infrastructure, on Tuesday, February 28th, 2023 GitHub Pages sites that contain symbolic links will no longer build outside of GitHub Actions.

The majority of Pages sites will not be affected by this change since building with GitHub Actions is the default. If any of your Pages sites is affected, you will receive a build failure email with instructions how to fix the error on your next build.