Add BUILD_ASSETS_IMAGE CI variable
What does this MR do?
Adds a variable to allow disabling of the build of the GitLab assets image.
Useful for people who are building from forks without the container registry enabled.
What are the relevant issue numbers?
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Documentation created/updated
- Tests added for this feature/bug
- Conforms to the code review guidelines
- Conforms to the merge request performance guidelines
- Conforms to the style guides
- Conforms to the database guides
- Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.