General Motors Co (GM.N) will cut 500 jobs as a shift is eliminated at a plant near Detroit that makes weak-selling small cars, the company said on Friday. The decision comes a day after GM said it would add 1,200 jobs and a shift at the Detroit-Hamtramck plant. The shift at the small-car Lake Orion plant near Detroit will end by early next year, and the new shift at the Detroit-Hamtramck plant will begin in the first quarter, GM said.