Wasn't recursing into args of extern calls while flattening
Wasn't recursing into args of extern calls while flattening


Former-commit-id: 6ddb1dbb860b0aafc002f78736704603c08c3d2e
Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide