Smashing Pumpkins’ Billy Corgan looked for inspiration at “Godspell” at the Circle in the Square on Sunday night. Disguised in a lumberjack hat, he watched with a blond female companion. Corgan recently told The Post’s Dan Aquilante he wants to write for Broadway, “but I want to be a better songwriter before I try Broadway and I wouldn’t allow one of my old songs [to be used]. If I do Broadway, I’m not coming to write three-chord rock songs.”