RFR: 7903790: Use source instead of release option for library compilation [v3]

[Jonathan Gibbons]

On Mon, 19 Aug 2024 16:45:38 GMT, Christian Stein <cstein at openjdk.org> wrote:

>> Please review this change to use `--source=N` instead of `--release=N` in order to prevent compiler errors reading `exporting a package from system module java.base is not allowed with --release` when compiling a library using preview features, enabled via the new `LIBRARY.properties` configuration file.
>
> Christian Stein has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update comment

Some self-tests would be nice.

We should not just rely on testing by using JDK.

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Marked as reviewed by jjg (Lead).

PR Review: https://git.openjdk.org/jtreg/pull/221#pullrequestreview-2249222898