https://roundcube.net/news/2019/11/09/roundcube-1.4.0-released
* `curl` cmd in the test can fail as roundcube returns a http/401 if
unauthorized (and we're explicitly requesting the login form). By
checking if the `persistent_login` plugin is loaded, the assertion is
still valid)
* Use `$argv[0]` to determine install path in the installer script. I'm
not exactly sure why, but it seems as `__DIR__` now resolves symlinks
which breaks the installer if roundcube is in a `buildEnv` with
third-party plugins.
With this option it's possible to specify a custom expression for
`roundcube`, i.e. a roundcube environment with third-party plugins as
shown in the testcase.
