Change SHA256 hash & exit script if error (#1789)
Change SHA256 hash & exit script if error (#1789)

* Change SHA256 hash & exit script if error

- set -e exits the script if a command exits with non-zero exit code (like checksum failure)

* Use shasum instead of sha256sum

* Check if shasum available, if it is, use it to verify checksum and fail if error

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