sysutils/orch: pull in some patches following portability testing

These were deemed critcial enough to be worth backporting: the first
issue affects spawn() of paths that look relative; these are now just
using $PATH, and the script's directory is prepended to $PATH.

The other is that the tests weren't easily runnable, so it's gained some
bits to improve that and we hook up TEST_TARGET in the ports tree here.