Return value

Need to send the return value from the tested shellcode so we can test for error values for things where there aren't observable side-effects (e.g. setuid without root)

Start by locating the shellcode testing harness in the pwntools-regression repository and trace how tested shellcode currently reports results. Determine where a return value can be captured and how error values should be exposed to tests. Done means tests can verify return values for cases without observable side effects, such as setuid without root.

Written by the indexing model from the issue text.