Actually, it's more common than you think for a major brand to design a car and outsource the building to a third party or even to outsource the whole design and development of a model entirely.
For example, Magna Steyr builds the E-Pace for Jaguar, the Countryman for Mini and the G-Wagon for Daimler in Graz, Austria. It also developed several cars on behalf of manufacturers such as the Audi TT, Fiat Bravo and Peugeot RCZ[1].
There were even rumors in Graz that execs from Cupertino have flown here to discuss the possibility of Magna building a car for Apple.