Well, I think it mostly depends on the order:

´Copy to Clipboard   |   Cancel´

or

´ Ok   |   Copy to Clipboard´

Personally I would prefer to have Copy as default button, given that the user wants to get the build information. If no textbox exists the offer is shown to copy to the clipboard instead. If he decides against it, the action needs to be canceled. So ´Cancel´ would have to be pressed. Using ´Ok´ here would be misleading IMO.