Slightly better error message for when you try to enable tracing on the GPU
Slightly better error message for when you try to enable tracing on the GPU

In the future it is possible to make this work.


Former-commit-id: 4e9f494ea48ad2e16988559b0168fd2e78dd659e
Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide