Add check for build args

[marohrdanz]

As of 2.24.2, we are using docker's build arguments to set the GIT_COMMIT and GIT_LATEST_TAG to be used by the ant build in the Dockerfile.

Since it's very easy to forget to set these, and end up with "${env.GIT_COMMIT}" and "${env.GIT_LATEST_TAG}" in the build artifacts, add a check in the Dockerfile to error if these build arguments are not set.

E.g.

RUN test -n "${GIT_COMMIT}" || (echo "Build argument GIT_COMMIT must be set" && false) 
RUN test -n "${GIT_LATEST_TAG}" || (echo "Build argument GIT_LATEST_TAG must be set" && false)