The definition of the male sex is XY (or XYY in rare cases). Differentialy responses to Androgen can occur on a such a chromosomal make up, but that is simply the definition of male. Is Caster Semenya XX (female) or XY?
Simple as that.
Editor's update on 5/2/2019. We realize google is sending a lot of people to this thread. The answer is, "Yes she's XY" as explained here: