scala-cli-action always install Java, even if JAVA_HOME is defined

[adamw]

The action shouldn't install Java if one is already installed, but this doesn't happen. That's probably because the default value for jvm is temurin:17, so that's always installed, unless the option is overriden.

The work-around is to provide an empty value for jvm:

    - name: Install scala-cli
      uses: VirtusLab/scala-cli-setup@main
      with:
        jvm: ''

[adamw]

Btw., the image above corresponds to the following config:

    - name: Install scala-cli
      uses: VirtusLab/scala-cli-setup@main