You can buy it, and there is a duty free shop (with alcohol) just before the exit of the airport at baggage claim hall), after immigration, just to confirm that you can buy it.
My commentary: I do not think it is the best gift (especially if bought in a duty-free). It is nearly as just giving money. Nothing personalized or something you think. Also it is not the best way to show respect to a guest country (and Dubai is much more liberal, but if your friend lives in an nearby emirate (less permissive) [a lot of people working in Dubai live in another emirate], it is not nice.
If you want to gift him something alcoholic, check something he could miss from UK (so something seldom, or in any case not from the well known brands you see everywhere). Food items that you cannot find easily in UAE is another option.