it works

.gitignore

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+result

flake.lock

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+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "freeorion-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1755374471,
+        "narHash": "sha256-T+6hTlu/dZnXICe5XMaQnKOXQxw5YTrrLUbyzCKA3mk=",
+        "owner": "freeorion",
+        "repo": "freeorion",
+        "rev": "e1080068ffff83bd53c27058801aed72cff0f3a1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "freeorion",
+        "repo": "freeorion",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1735563628,
+        "narHash": "sha256-OnSAY7XDSx7CtDoqNh8jwVwh4xNL/2HaJxGjryLWzX8=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "b134951a4c9f3c995fd7be05f3243f8ecd65d798",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-24.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "freeorion-src": "freeorion-src",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "Flake for building FreeOrion (master branch)";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+    flake-utils.url = "github:numtide/flake-utils";
+    freeorion-src.url = "github:freeorion/freeorion";
+    freeorion-src.flake = false;
+    # Optionally, pin to a commit: url = "github:freeorion/freeorion/COMMIT";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, freeorion-src }: 
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+
+        buildInputs = with pkgs; [
+          cmake
+          git
+          python310
+          pkg-config
+          boost
+          python310Packages.boost
+          zlib
+          freetype
+          libpng
+          libvorbis
+          libogg
+          openal
+          SDL2
+          glew
+        ];
+        nativeBuildInputs = with pkgs; [
+          cmake
+          git
+          pkg-config
+          makeWrapper
+        ];
+      in
+      {
+        packages.freeorion = pkgs.stdenv.mkDerivation {
+          pname = "freeorion";
+          version = "unstable"; # or use date/commit
+          src = freeorion-src;  # Use flake input as src
+
+          buildInputs = buildInputs;
+          nativeBuildInputs = nativeBuildInputs;
+
+          cmakeFlags = [
+            "-DCMAKE_BUILD_TYPE=Release"
+            "-DBUILD_TESTING=Off"
+            "-DCMAKE_INSTALL_RPATH=$out/lib"
+            "-DCMAKE_BUILD_WITH_INSTALL_RPATH=ON"
+          ];
+
+          doCheck = false;
+
+          installPhase = ''
+            # mkdir -p $out/bin
+            # cp /build/source/build/freeorion $out/bin
+            # cp /build/source/build/freeorionca $out/bin
+            # cp /build/source/build/freeoriond $out/bin
+            cmake --install . --prefix=$out
+            wrapProgram $out/bin/freeorion --set LD_LIBRARY_PATH "$out/lib/freeorion:${pkgs.stdenv.cc.cc.lib}/lib"
+          '';
+
+          # postFixup = ''
+          #   patchelf --set-rpath $out
+          # '';
+          
+          meta = with pkgs.lib; {
+            description = "FreeOrion, a free, open source, turn-based space empire and galactic conquest game";
+            homepage = "https://www.freeorion.org/";
+            license = licenses.gpl2Plus;
+            maintainers = with maintainers; [ ];
+            platforms = platforms.linux;
+          };
+        };
+        defaultPackage = self.packages.${system}.freeorion;
+      });
+}