I thought of that. I can often extract MSIs using 7zip. I was about to download until I read that it can only be used for development purposes. Apparently I have to agree not to redistribute it. No thanks Red Hat.
Elsewhere in this thread I discovered:
https://github.com/ojdkbuild/ojdkbuild
And I already knew about:
http://www.azul.com/downloads/zulu/
The more OpenJDK folders I have to test against (on both Linux and Windows), the better. Just change environment variables.
You should be able to extract an msi with the right msiexec command line switches.