Add nix flake and lock file. Add nix build step. Pending nix flake up…

…date step

.github/workflows/nix-github-actions.yml

@@ -0,0 +1,13 @@
+name: "build nix flake"
+on:
+  pull_request:
+  push:
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+       submodules: true
+    - uses: cachix/install-nix-action@v25
+    - run: nix build '.?submodules=1'

flake.nix

@@ -0,0 +1,44 @@
+{
+  description = "A nix flake for the Yosys synthesis suite";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+        customYosys = pkgs.clangStdenv.mkDerivation {
+          name = "yosys";
+          src = ./. ;
+          buildInputs = with pkgs; [ clang bison flex libffi tcl readline python3 llvmPackages.libcxxClang zlib git ];
+          checkInputs = with pkgs; [ gtest ];
+          propagatedBuildInputs = with pkgs; [ abc-verifier ];
+          preConfigure = "make config-clang";
+          checkTarget = "test";
+          installPhase = ''
+            make install PREFIX=$out
+          '';
+					buildPhase = ''
+          make -j$(nproc)
+          '';
+          meta = with pkgs.lib; {
+            description = "Yosys Open SYnthesis Suite";
+            homepage = "https://yosyshq.net/yosys/";
+            license = licenses.isc;
+            maintainers = with maintainers; [ ];
+          };
+        };
+      in {
+        packages.default = customYosys;
+        defaultPackage = customYosys;
+        devShell = pkgs.mkShell {
+          buildInputs = with pkgs; [ clang bison flex libffi tcl readline python3 llvmPackages.libcxxClang zlib git gtest abc-verifier ];
+        };
+      }
+    );
+}