Support building nextpnr with nix flakes

.gitignore

@@ -43,3 +43,4 @@ install_manifest.txt
 *.phys
 *.dcp
 *.bit
+result

flake.nix

@@ -0,0 +1,69 @@
+{
+  description = "A flake for the nextpnr FPGA place and route tool";
+
+  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;
+          overlays = [];
+        };
+        # Define custom overrides or additional packages
+        myPythonPackages = pkgs.python3Packages.override {
+          overrides = self: super: {
+            apycula = super.apycula.override {
+              # Place any necessary overrides here
+            };
+          };
+        };
+        enableGui = false;
+      in
+      {
+        packages = {
+          nextpnr = pkgs.stdenv.mkDerivation {
+            pname = "nextpnr";
+            version = "0.6";
+            src = ./.;
+
+            nativeBuildInputs = [ pkgs.cmake ]
+              ++ (pkgs.lib.optional enableGui pkgs.qt6.wrapQtAppsHook);
+            buildInputs = [
+              (pkgs.boost.override { python = pkgs.python3; enablePython = true; })
+              pkgs.python3
+              pkgs.eigen
+              myPythonPackages.apycula
+              pkgs.icestorm
+              pkgs.trellis
+            ] ++ (pkgs.lib.optional enableGui pkgs.qt6.qtbase)
+              ++ (pkgs.lib.optional pkgs.stdenv.cc.isClang pkgs.llvmPackages.openmp);
+
+            cmakeFlags = [
+              "-DARCH=generic;ice40;ecp5;gowin"
+              "-DBUILD_TESTS=ON"
+              "-DICESTORM_INSTALL_PREFIX=${pkgs.icestorm}"
+              "-DTRELLIS_INSTALL_PREFIX=${pkgs.trellis}"
+              "-DTRELLIS_LIBDIR=${pkgs.trellis}/lib/trellis"
+              "-DGOWIN_BBA_EXECUTABLE=${myPythonPackages.apycula}/bin/gowin_bba"
+              "-DUSE_OPENMP=ON"
+              # warning: high RAM usage
+              "-DSERIALIZE_CHIPDBS=OFF"
+            ] ++ (pkgs.lib.optional enableGui "-DBUILD_GUI=ON");
+
+            meta = with pkgs.lib; {
+              description = "Place and route tool for FPGAs";
+              homepage = "https://github.com/yosyshq/nextpnr";
+              license = licenses.isc;
+              platforms = platforms.all;
+              maintainers = with maintainers; [ thoughtpolice emily ];
+            };
+          };
+        };
+
+        packages.default = self.packages.${system}.nextpnr;
+      });
+}