[ci] ensure shell script exit codes are in range 0-255

[jameslamb]

This PR proposes replacing uses of exit -1 in shell scripts with exit 1.

Benefits of this change

Removes reliance on shells correctly handling exit -1 (which is technically not recommended by e.g. bash) in the project's scripts.

Notes for Reviewers

From the bash docs (link)

Exit statuses fall between 0 and 255

And from the shellcheck docs (SC2242)

Note in particular that exit -1 is equivalent to exit 255, but that exit 1 is the more canonical way of expressing the first possible error code.

This change resolves the following error from shellcheck:

SC2242 (error): Can only exit with status 0-255. Other data should be written to stdout/stderr.