I don't know - one of these days I'll finally get the guts to change my laptop's language to Polish.
Fortunately, this rule only applies to the past and future tenses, so you're safe if you can keep to present tense.
The only translations I've worked with have been Facebook-based, where, by and large, the person's gender is already known.
Elsewhere, I've seen things written in a bit of a hacky manner, e.g. the above written as: Właśnie wygrałeś/aś.