Docker build task doesn't track any inputs #50125
Description
PR #49613 changed the Docker build to avoid rebuilding if the outputs are up-to-date. However, the build task isn't tracking any inputs here. For example, after running assemble, if you change the Dockerfile, things are still UP-TO-DATE, which is clearly incorrect. We should be tracking the Dockerfile, as well as anything else we include in the image as inputs to this task otherwise folks are liable to get unreliable behavior.
Originally posted by @mark-vieira in #49613 (comment)