Options feature does not allow adding extra xvfb-run options

[ssbarnea]

The way options feature was implemented does not allow adding other arguments to xvfb-run itself, like enabling an error log.

Usually you would have to add something like -e /tmp/x.logto xvfb-run to enable logging instead of the implicit /dev/null but we cannot do that using options because the composed command will become /usr/bin/xvfb-run --auto-servernum -s -e x.log ...

The -s being before our extra options breaks it and I am not aware of a way to address that.