This change:
- Fixes some warnings reported by [Shellcheck][0]. Notably, if your repo
is in a folder with a space (e.g., `/Users/foo/My Code/Signal-iOS`),
this script wouldn't work.
- Adds `set -u` to error when using unbound variables, in case we make a
mistake
- Adds `set -o pipefail` to error if piping fails. Not used by this
script, but I put this line in all my shell script just in case
Tested this when taking 5.37.0 to production and it worked fine.
[0]: https://www.shellcheck.net/
