Prior to this commit some helper scripts used hardcoded paths to
`/bin/sh` and `/bin/bash` in script shebangs. This will error on systems
that don't place `bash` in `/bin/` (e.g. NixOS).
This commit updates the scripts to use `/usr/bin/env` to find `bash`
based on the user's `$PATH`. This has better portability and allows the
scripts to run without err (or specifying an interpreter explicitly) on
systems with atypical `bash` installs.
Daniel McCarney