The ENV vars are used while building the container, instead of proper arg vars.
If arg vars are used, they can be overwritten while building the container using "--build-arg" effectively allowing to change the command executed in the "RUN" part, as run is only executed at container build time and not at Instantiation time.
@agowa338 Thanks for your pr!
I have squashed the comments and added some more changes for the update to 1.4.0p19 ... your changes have been included with the pr #15
The ENV vars are used while building the container, instead of proper arg vars. If arg vars are used, they can be overwritten while building the container using "--build-arg" effectively allowing to change the command executed in the "RUN" part, as run is only executed at container build time and not at Instantiation time.