Terrell McLean, the co-owner and chef at Bubby s BBQ, sprays down racks of ribs on his giant smoker, Goliath. There’s a hulking new fixture in the South Wedge that you’ll smell before you see, whose aroma of wood fire and seasoned, slow-cooking meats will have barbecue lovers floating Looney Tunes-style to its source in a courtyard near the corner of South and Alexander. That would be “Goliath,” an imposing, custom-built smoker whose 500-gallon drum and charcoal black smokestack is the star attraction of Bubby’s BBQ, which opened in December in the storefront that had been John’s Tex Mex.