Add pre-merge tests that use a WSL runner
Description
This MR adds a test run using a runner that is on WSL, skips sandbox tests and includes miscellaneous fixes.
The gitlab runner is currently running on a VM on a computer provided by Codethink, but a script to configure the runner from scratch is available at https://gitlab.com/jonathanmaw/wsl-setup-script.
Changes proposed in this merge request:
- In .gitlab-ci.yml, add a test that is run on a WSL runner.
- Skip tests that use a sandbox on Windows (previously sandbox tests expected to run on any platform except a linux that is lacking bubblewrap)
- Fix tests that are broken by running on WSL
This merge request, when approved, will close: #852 (closed)