GPU backend

Adds GPU backend and "CUDA" feature to all the tests. As of MR creation, there were no forks in tested IRs so only vanilla non-parallel (single block, single thread) codegen has been tested.

hercules_opt/src/pass.rs

@@ -1017,9 +1017,6 @@ impl PassManager {
                         let mut nvcc_process = Command::new("nvcc")
                             .arg("-c")
                             .arg("-O3")
-                            .arg("-lcudart")
-                            .arg("-L/usr/lib/x86_64-linux-gnu")
-                            .arg("-L/usr/local/cuda/lib64")
                             .arg("-o")
                             .arg(&cuda_object)
                             .arg(&cuda_path)