There's no implementation of execvp() on Fuchsia, so attempt to emulate
it in `run_with_crashpad` by using launchpad. Failures are mapped to
exit codes similar to what the execvp() path would return for missing
binary, and other non-subprocess errors.
Bug: crashpad:196
Change-Id: I042cbcf82bfd4560442a9d7f301e97bbfea54042
Reviewed-on: https://chromium-review.googlesource.com/1038055
Commit-Queue: Scott Graham <scottmg@chromium.org>
Reviewed-by: Joshua Peraza <jperaza@chromium.org>