Use param files to invoke process_target.py

[mrkkrp]

Without a param file invocations fail with "Argument list too long" when run on larger projects.

[martis42]

@mrkkrp
Thanks for this contribution.
One minor question though. Is there a specific reason why you set use_always? I do not exactly have a problem with this, but would like to understand why the default behavior is not sufficient,

[mrkkrp]

Well, one reason is testing. Without use_always I think your test suite would not exercise the code that this change introduces. Another reason is that I simply did not trust Bazel to switch between behaviors correctly (which is just me being paranoid) and in general I do not like having 2 possible branches of execution with regard to how arguments are passed. Happy to remove use_always if desired!