More improvements to the release scripts.

• Add a 'dev' option to the mac bundle that's much faster, intended to quickly test bundle-like behaviour.
• Add an option to only archive the 'mod' folder, intended to speed up the CI weekly builds and avoid taking too much disk

space.

• Tweak the windows installer, add an option to create a shortcut to the desktop (Fixes #1637). This uses the readme 'hack' which appears to be a relatively standard way of doing that.
• Make the scripts executable.
• Update jenkinsfile.

Follows rP24343

Differential Revision: https://code.wildfiregames.com/D3191