By looking at where things are made rather than by using hedonic adjustments to multiply up INTC revenue until it hides the problem (or whatever the strategy is today now that INTC is flagging).
Assembly is one example of manufacture, so that distinction isn't really the one you think it is. Output is tracked by value added, so the mythical "car comes missing a single bolt which gets added in Flint" doesn't really show up in the output numbers, if that's your worry.