Add nix devShell with deps for the /syn yosys synthesis job

flake.nix

@@ -101,11 +101,18 @@
       '';
     };
 
+    syn_shell = shell.override (prev: {
+      name = "ibex-devshell-synthesis";
+      nativeBuildInputs = prev.nativeBuildInputs ++ ibex_syn.deps;
+      shellHook = prev.shellHook + ibex_syn.profile;
+    });
+
   in {
     devShells.${system} = {
       default = inputs.self.devShells.${system}.shell;
 
       inherit shell;
+      inherit syn_shell;
     };
   };
 }

nix/syn.nix

@@ -0,0 +1,52 @@
+# Copyright lowRISC Contributors.
+# Licensed under the MIT License, see LICENSE for details.
+# SPDX-License-Identifier: MIT
+
+# Deps for Ibex synthesis jobs
+
+{
+  inputs,
+  pkgs,
+  ...
+}: let
+
+  sv2v_local = import ./sv2v.nix {inherit inputs pkgs;};
+
+  ibex_syn_deps = [
+    sv2v_local.default
+  ] ++ (with pkgs; [
+    # haskellPackages.sv2v # broken
+    yosys
+    openroad
+  ]);
+
+  # Create a dumb package of nangate45
+  # > All we need is a path to the sources
+  nangate45 = pkgs.stdenv.mkDerivation rec {
+    pname = "openroad-nangate45";
+    version = "PDKv1.3_v2010_12.Apache.CCL";
+    src = pkgs.fetchFromGitHub {
+      owner = "The-OpenROAD-Project";
+      repo = "OpenROAD-flow-scripts";
+      rev = "181e9133776117ea1b9f74dbacbfdaadff8c331b"; # Tag: v3.0
+      hash = "sha256-fYAdhBsMcuCXmPMQVCRdm75Tk0rd9zLnLfJdjhnhC00=";
+    };
+    sourceRoot = "${src.name}/flow/platforms/nangate45";
+    phases = [ "unpackPhase" "installPhase" ];
+    installPhase = ''
+        mkdir -p $out
+        cp -r ./* $out
+      '';
+  };
+
+  ibex_syn_profile = ''
+    export LR_SYNTH_CELL_LIBRARY_NAME=nangate
+    export LR_SYNTH_CELL_LIBRARY_PATH=${nangate45}/lib/NangateOpenCellLibrary_typical.lib
+  '';
+
+in {
+
+  deps = ibex_syn_deps;
+  profile = ibex_syn_profile;
+
+}