The artists who inspired Finneas' debut solo album 'Optimist' may surprise you Enlarge this image toggle caption Luke Fenstermaker/Courtesy of the artist Luke Fenstermaker/Courtesy of the artist Set List "What They'll Say About Us" "A Concert Six Months From Now" "Hurt Locker" "Only A Lifetime" When I sat down to talk with Billie Eilish, she said this about her producer, …