fix artifact file ownership inside container builds

[FredrikHson]

this fixes an issue that occurs when you use an image without root as the user
artifacts being copied into the container as the user outside of the container so changing the artifacts/anything in contained folders will fail due to permission denied
example dockerfile+gitlab-ci.yaml should fail on the dep step without this patch and work after

FROM rockylinux:9
RUN useradd build
USER  build

--- 
build:
  stage: build
  artifacts:
    paths:
      - build
  image:
    name: rockyuser
  script:
    - mkdir -p build/river
    - echo "version=1.0.0" > build/river/release

dep:
  stage: deploy
  dependencies:
    - build
  tags:
    - on-prem
  image:
    name: rockyuser
  script:
    - id -g
    - id -u
    - ls -lah build
    - mkdir -p build/road
    - echo "version=1.1.1" > build/road/release

---

Summary by cubic

Fixes permission errors in non-root container builds by ensuring artifacts and the project directory are owned by the container user. We detect the image’s UID:GID and apply it when copying files and setting permissions.

• Bug Fixes
  • Detect UID:GID via id -u:id -g from the job image and reuse it across steps.
  • Chown/chmod the project dir and /tmp in the helper using the detected owner.
  • Copy build files via a tar stream with --owner/--group to ensure correct ownership inside the container.

^{Written for commit d80d1c6. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

[firecow]

Please attach some performance charts. I'm worried this would kill performance in big projects.