Support `--eval` command line argument that evaluates one expression then exit

[cireu]

I found it's quite helpful if Chez can provide such command line argument to run some quick command (especially in the packaging Chez related package)

chez-scheme --eval '(begin (compile-libraries ...))'

It may arguably that this can be done via

echo '(begin (compile-libraries ...))' | chez-scheme -q

(or just write your command to temporary file then execute it via chez-scheme --script)

However, support --eval command line argument is still useful for the use case that pipe(creating temporary file) is not reliable/not convenient.

I create this issue to request your comments, I'd like to try implement it and send a PR if there could be positive feedback

[funk443]

Ya, I think it'll be helpful. Many Scheme/Lisp compilers have this flag, too.