This option allows to install an additional JDK without making it the
default one.
I have wanted this for quite a long time as I'm running custom GitHub
Actions with Java, which might require a specific JDK and I don't want
to pollute the JDK that is used by the overall workflow calling the
action.
And I'm apparently not alone as there was a preexisting issue.
Fixes#560
33aba78939