NEW YORK — Activist investor Bill Ackman’s Pershing Square Capital Management has taken a stake of about $1 billion in Lowe’s Cos., joining hedge fund D.E. Shaw which invested in the company earlier this year. A source told CNBC that Ackman is not seeking a seat on Lowe’s board of directors. Ackman himself said he supports the company’s management, including new CEO Marvin Ellison, who was named this week after being wooed from the same position at JC Penney. Pershing Square declined to say whether it was involved in the return of Ellison, once executive VP of U.S. stores at Home Depot, to the home improvement sector.