README symlinks and redirect loop

Notes:

• New way of dealing with symlinks !1499 (merged)
• Backwards compatible (attempt) !1567 (merged)
• We use the same underlying Docker image https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/dockerfiles/Dockerfile.builder.onbuild, so the change had to be backwards compatible, this is why I added https://gitlab.com/gitlab-org/gitlab-docs/-/blob/e760708542575c2040d32b81b92422bf44a85733/scripts/normalize-links.sh#L84-96

It seems the command to symlink all readmes is run even in cases it shouldn't be https://gitlab.com/gitlab-org/gitlab-docs/-/jobs/1287130014#L3879.

Solution

Found in #1035 (comment 601537229). The builder-onbuild Docker image hadn't been updated.