Need a test for processAttach without the executable

[cuviper]

A regression was found in dyninst/dyninst#146 that attaching to a process without specifying the executable was broken. The documentation for Process::attachProcess does state that the executable is optional. AFAICS this is never tested anywhere.

It's not clear to me the best way to add this. Currently, all tests can run in either create or attach mode. It seems undesirable to add an entire test matrix of attach-no-exe. Is there a good way to write a targeted attach test for this?

[wrwilliams]

Seems like this should be a variant on the basic proccontrol test (pc_launch)--either we use a custom setup/teardown path, or we add an extra process when pc_launch is running in attach mode. Also, we should most likely change the proccontrol fixtures so that attach defaults to the minimal default, and the extra testing is of attach with arguments.