Default to Docker build when `--dockerfile` is set

[mnafees]

Pull request type

Please check the type of change your PR introduces:

• [ ] Bugfix
• [ ] Feature
• [x] Other (please describe): Improvement

Pull request checklist

Please check if your PR fulfills the following requirements:

• [x] If it's a backend change, tests for the changes have been added and go test ./... runs successfully from the root folder.
• [ ] If it's a frontend change, Prettier has been run
• [ ] Docs have been reviewed and added / updated if needed

What is the current behavior?

Method can be pack even when --dockerfile is set.

What is the new behavior?

Default to Docker build method when --dockerfile is set.

Technical Spec/Implementation Notes