Update OpenVersion task

[Leguan16]

I updated the open task to reflect the new build script.

It still won't work for all versions because it fails to parse the MacheMeta file because older versions have missing fields. But it should work for recent versions post #4. I don't know what the best way would be to fix that problem, so I didn't touch it for now.

I also don't know if a template is preferred over a builder.

I tested it with 1.21.3 and it works perfectly.