RFR: 7903187: jextract should support --version option [v2]

[Athijegannathan Sundararajan]

On Fri, 13 May 2022 15:34:45 GMT, Athijegannathan Sundararajan <sundar at openjdk.org> wrote:

>> added --version option that prints the underlying Java version and exits.
>
> Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   adding more info to version output per review recommendation

I'll piggyback adding --version to README.md in the next change.

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PR: https://git.openjdk.java.net/jextract/pull/31