[lworld] RFR: 8372515: [lworld] Plumb in javac flags for compiling with preview mode [v2]

[David Beaumont]

On Wed, 10 Dec 2025 10:15:34 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> OK, I see -- this is an "hidden" option, just used internally by javac to communicate to the file manager whether preview mode should be enabled or not. I now see the same pattern being used as that for multirelease jars.
>
> Yes - we need a separate option, as (AFAIK) the current framework does not allow options to be used both for and outside of file managers.
> 
> We more or less need to send the preview mode using an option/`handleOption`, as the file manager may be a file manager provided by the user, and only delegate to `JavacFileManager`. That's the same reason why `--multi-release` is used for file managers.

If either of you think an additional comment would help future maintainers here, let me know what it should be.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1761#discussion_r2622813360