Don't return the pipeline
Don't return the pipeline

This makes edit-compile-run iterations work without it complaining about
retaining references to the old version of the function


Former-commit-id: 287c72fedd15b157492c8f21084f2731698aab06
darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide