Provide an --argfile commandline option for the batch compiler

Arguments to the ejc batch compiler can become long. Some system (e.g. linux) impose a limit for the maximum number of arguments one can pass to a process.

For this purpose, it would be good to have an option `--argfile` that when passed to ejc is interpreted as a text file with the system encoding that contains one argument on each line.

This currently blocks
- https://github.com/eclipse-tycho/tycho/issues/1358