added cli options

relay.nix

@@ -0,0 +1,21 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.rustPlatform.buildRustPackage {
+  pname = "relay";
+  version = "0.1.0";
+  src = ./.;
+
+  cargoLock = {
+    lockFile = ./Cargo.lock;
+  };
+
+  cargoBuildFlags = [ "-p" "relay" ];
+
+  nativeBuildInputs = [ pkgs.makeWrapper ];
+  buildInputs = [ pkgs.ghdl-llvm ];
+
+  postFixup = ''
+    wrapProgram $out/bin/relay \
+      --prefix PATH : ${pkgs.lib.makeBinPath [ pkgs.ghdl-llvm ]}
+  '';
+}