Script generator: Add manual test for standalone script generator (VM not a good solution)

As a user I want to be able to use the script generator standalone, without having to worry about installing git or python. The standalone script generator is designed to be used in this way, packaging git and python with it. Every release we should verify that this reqirement is fulfilled by running a system test, possibly manually using a blank VM.

## Acceptance criteria
- [ ] The standalone script generator is tested every release for its lack of dependence on preinstalled third-party software

## Notes

#5700 was an issue which could have been caught by such a test