builder: some small fixups + fix a bug where empty entrypoints would not override inheritance.

closes #8732. I also tacked on some spelling fixes and a formatting change to debug logging. There is a test as well.

The crux of the issue is multi-tiered:

* in the parser, in single word cases (remember, `[]` evaluates to no content), the attributes and "original" line did not propagate to the evaluator.
* in runconfig, merging the image settings into the new builder settings would not distinguish between `nil` and an empty array.
* in the `entrypoint` evaluator, the switch statement would eagerly treat nil and empty arrays as equal regardless of how they were defined.