[orchestrate] Support both relative & absolute paths to ffx

Change-Id: Ief43cb918de870025fb2f999ff814100950333e8
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1630124
Reviewed-by: Zijie He <zijiehe@google.com>
Reviewed-by: Darren Chan <chandarren@google.com>
Commit-Queue: Jerry Belton <jcecil@google.com>
2 files changed