Feature Proposal: Toggle to disable boot jdk downloads in the build scripts

[adamfarley]

Summary

An argument or flag that causes the build scripts to deliberately disable automatic boot jdk downloads (which potentially risk build security).

Purpose of this Issue

• [x] 1) To establish the mechanism for triggering the inhibition of said functionality.
• [x] 2) To unify file downloads (in the build process) through a single part of the code base.
• [ ] 3) To make 1 inhibit 2.