Once JustJ supports riscv64, to reset Jenkinsfile to use it as native jdk.

[jonahgraham]

Once JustJ supports riscv64, to reset Jenkins to use it as native jdk

[jonahgraham]

@yuzibo I split this out of #2310 for the remaining checklist item. Can you review at your convenience please.

[yuzibo]

@jonahgraham Thank you! yeah, this is a change that we need to pay attention to and I will look at it continuely.

[HannesWell]

In fact this is already possible since JustJ provides JDK-17 for linux.riscv64.
It hasn't be done yet, since for Windows on ARM Temurin only provides JDK-21 and higher and consequently JustJ does the same.
And since the change is similar for win32.aarch64 and linux.x86_64 I wanted to remove the workaround for both platforms at the same time, when the Eclipse SDK requires Java-21, which is probably soon.