Add directive packaging.graalvmJvmId

[zrhmn]

Fixes #4222

Add graalvmJvmId param to the Packaging class in scala.build.preprocessing.directives.
Add relevant @DirectiveExamples and @DirectiveUsage.
Add test at scala.build.tests.PackagingUsingDirectiveTests validating that graalvmJvmId gets passed to nativeImageOptions.

Checklist

• tested the solution locally and it works
• ran the code formatter (scala-cli fmt .)
• ran scalafix (./mill -i __.fix)
• ran reference docs auto-generation (./mill -i 'generate-reference-doc[]'.run)

How much have your relied on LLM-based tools in this contribution?

I relied moderately on GitHub Copilot. Since I am not a regular developer, it was hard for me to manually browse the codebase, until I ask the Copilot chat for help locating where directives were defined. Making the code change was easy without copilot help because the case class Packaging code was pretty readable and self-explanatory. Then I had to ask Copilot where to add tests, and finished the tests with Copilot-autocomplete.

How was the solution tested?

I created a project with the following directives:

//> using packaging.packageType graalvm
//> using packaging.graalvmJvmId graalvm-java25:25.0.2
//> using packaging.output "sctest01"
//> using packaging.graalvmArgs --no-fallback

... and ran with the built binary

../scala-cli/out/cli/3.3.7/standaloneLauncher.dest/launcher --power package .

(sans the graalvm-jvm-id arg) and it compiled, showing version GraalVM CE 25.0.2+10.1 during compilation. If I repeat this with the scala-cli installed on my system, I get GraalVM CE 17.0.9+9.1 instead, which confirms that the built launcher exhibits desired behavior.

Additional notes

[zrhmn]

Hi @Gedochao I'm wondering if graalvmVersion and graalvmJavaVersion should also be directives? It seems just a matter of passing the parameters to the Packaging case class. I am torn because on the one hand, it would be consistent -- all the graalvm* args would also be directives, but on the other hand, I think it may clutter the docs too much. Just graalvmJvmId suffices for my own needs, but I wanna get outside opinions. What do you think?

[zrhmn]

I would also appreciate some help figuring out why the CI is failing.