- Enable tests for osx.universal platform.
- Export HTML5 (but skip upload as .cast files aren't exported
properly).
- HACK: Use HTML5 export to generate .import directory for tests
This way we don't get an error message even if using
`continue-on-error` set to `true`.
In a freshly cloned repo, submodule directories exist but are not
empty. Check if they are empty and update submodules. Previously,
submodules where only updated if their directories did not exist.
