Update BuildKit docs for rootless runner feedback

Lysanne Pintorequested to merge
549941-buildkit-feedback-docs into master

What does this MR do and why?

Updates the rootless BuildKit documentation to address user feedback that the examples fail or hang.

Changes:

  • Add a note that rootless builds still require a runner that permits the system calls BuildKit uses. GitLab.com hosted runners work without extra configuration; unprivileged self-managed Docker executors can fail.
  • Explain why the entrypoint: [""] override is required (the default image runs the daemon and the job hangs until timeout).
  • Add a troubleshooting entry for the operation not permitted and buildkitd.sock errors on unprivileged Docker executor runners, pointing to the runner security_opt setting and noting the seccomp:unconfined isolation trade-off.
  • Add a tip to reuse the predefined CI_SERVER_TLS_CA_FILE variable for custom CA certificates.

🔗 References

Edited by Lysanne Pinto

Merge request reports