Broadway tuner “Baby It’s You!” will shutter Sept. 4 after about five months on the boards.Produced by a team headed by Warner Bros. Theater Ventures and American Pop Anthology, “Baby It’s You!” — following the behind-the-scenes story of Florence Greenberg, who discovered ’60s girl group the Shirelles and steered the band to success — hoped to attract the same baby-boomer demo that has fueled B.O. at Rialto hit “Jersey Boys,” another bio-musical centered around golden oldies. “Baby It’s You!,” however, never quite caught on with auds or critics. Weekly sales have cracked the $500,000 mark only once, and over the last several weeks attendance has hovered between 70% and 80% of capacity. Last week the tuner rang in about $375,000 in sales. Earlier this summer the musical initiated Friday matinee performances in lieu of Wednesday evening shows in an effort to maximize biz from Tri-State visitors and matinee crowds.