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

…date step

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

@@ -0,0 +1,33 @@
+name: Nix Flake actions
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - main
+
+jobs:
+  nix-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v24
+      - id: set-matrix
+        name: Generate Nix Matrix
+        run: |
+          set -Eeu
+          matrix="$(nix eval --json '.#githubActions.matrix')"
+          echo "matrix=$matrix" >> "$GITHUB_OUTPUT"
+
+  nix-build:
+    needs: nix-matrix
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix: ${{fromJSON(needs.nix-matrix.outputs.matrix)}}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v24
+      - run: nix build -L ".#${{ matrix.attr }}"

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";
+		nix-github-actions.url = "github:nix-community/nix-github-actions";
+		nix-github-actions.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, nix-github-actions }:
+    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
+          '';
+          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 ];
+        };
+				githubActions = nix-github-actions.lib.mkGithubMatrix { checks = self.packages; };
+      }
+    );
+}