fix build without CUDA

src/drivers/cuda/starpu_cublas.c

@@ -80,8 +80,10 @@ void starpu_cublas_shutdown(void)
 
 void starpu_cublas_set_stream(void)
 {
+#ifdef STARPU_USE_CUDA
 	if (!_starpu_get_machine_config()->topology.cuda_th_per_dev ||
 		(!_starpu_get_machine_config()->topology.cuda_th_per_stream &&
 		 _starpu_get_machine_config()->topology.nworkerpercuda > 1))
 		cublasSetKernelStream(starpu_cuda_get_local_stream());
+#endif
 }