RFR: Update GHA to jdk20 [v6]

Mon Dec 12 16:12:10 UTC 2022

On Mon, 12 Dec 2022 15:51:40 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This PR updates the github actions on the jdk20 branch
>
> Maurizio Cimadamore has updated the pull request incrementally with four additional commits since the last revision:
> 
>  - Merge pull request #2 from JornVernee/MAC
>    
>    Get build working on Mac as well
>  - use JDK 17 for Gradle
>  - use JDK 19 for Gradle
>  - Add mac

.github/workflows/test.yml line 64:

> 62:       uses: oracle-actions/setup-java at v1.3.1
> 63:       with:
> 64:         release: 17

Maybe we could add a comment here that says that this sets `JAVA_HOME` for gradle to run on?

-------------

PR: https://git.openjdk.org/jextract/pull/96