The folder `json_info_files` contains multiple JSON files which describe
created firmware images. The folder is not removed between builds as the
ImageBuilder does not use `image.mk`.
Not removing the JSON files result in a merged `profiles.json` file
containing entries for outdated or non-existing images.
This commit adds the `json_info_files/` cleanup step to the ImageBuilder
Signed-off-by: Paul Spooren <email@example.com>