Incorrect SCRIPT_ARG handling for docker images

[nikic]

SCRIPT_ARG is provided via --build-arg when building the docker image. The same Dockerfile will be built with different SCRIPT_ARGs.

However, the IMAGE_TAG for the built images does not include this information. This means that the image in the registry will end up with a hardcoded SCRIPT_ARG that is basically chosen at random (I think).

This doesn't matter for CI, but it does mean that running jobs using SCRIPT_ARG locally using ci-tool will give unexpected results.

This could be fixed by including SCRIPT_ARG in the cache key, but TBH I don't understand why this one thing is using --build-arg at all, and not going through an environment variable like everything else.

@marcoieni @Kobzol

[nikic]

Basically, I'd expect docker/run.sh to pass --env SCRIPT="/tmp/${SCRIPT_ARG}" if SCRIPT_ARG is set.

[nikic]

I've put up #143964 with a possible fix.