cxx_mangling_gpu should be if(TARGET_PTX)
cxx_mangling_gpu should be if(TARGET_PTX)


Former-commit-id: 48daf610120cbf6a121e13d45b9f07e36fa2febf
darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide