[M7] flake: distribution bundles + non-NixOS wrapper

flake.nix

@@ -4,18 +4,39 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
     flake-utils.url = "github:numtide/flake-utils";
+    bundlers.url = "github:NixOS/bundlers";
+    bundlers.inputs.nixpkgs.follows = "nixpkgs";
   };
 
-  outputs = { self, nixpkgs, flake-utils }:
+  outputs = { self, nixpkgs, flake-utils, bundlers }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs { inherit system; };
 
+        # exec::run shells out to these at runtime; wrap the binary so
+        # they're reachable even outside a nix develop shell.
+        cargoxxRuntimePath = pkgs.lib.makeBinPath [
+          pkgs.nix
+          pkgs.cmake
+          pkgs.ninja
+          pkgs.curl
+          pkgs.git
+        ];
+
+        # Defaults applied to the bundled `nix` so it works on hosts
+        # that don't already have nix set up (Arch/Debian/Fedora users
+        # who install our .pkg.tar.zst / .deb / .rpm). Multi-user mode
+        # would expect a `nixbld` group and a running daemon
+        cargoxxNixConfig = ''
+          experimental-features = nix-command flakes
+          build-users-group =
+        '';
+
         cargoxx-bin = pkgs.gcc15Stdenv.mkDerivation {
           pname = "cargoxx";
           version = "0.1.0";
           src = ./.;
-          nativeBuildInputs = [ pkgs.cmake pkgs.ninja ];
+          nativeBuildInputs = [ pkgs.cmake pkgs.ninja pkgs.makeWrapper ];
           buildInputs = [ pkgs.sqlite pkgs.reproc pkgs.catch2_3 ];
           configurePhase = ''
             cmake -S build -B build/release -G Ninja \
@@ -27,6 +48,9 @@
           installPhase = ''
             mkdir -p $out/bin
             cp build/release/cargoxx $out/bin/
+            wrapProgram $out/bin/cargoxx \
+              --prefix PATH : ${cargoxxRuntimePath} \
+              --set-default NIX_CONFIG ${pkgs.lib.escapeShellArg cargoxxNixConfig}
           '';
           hardeningDisable = [ "all" ];
         };
@@ -103,8 +127,54 @@
             '';
             hardeningDisable = [ "all" ];
           };
+        bundlers-sys = bundlers.bundlers.${system};
+
+        # Arch's pacman expects a tar.zst archive containing a
+        # `.PKGINFO` metadata file plus the file tree rooted at /.
+        # We ship the entire closure under /nix/store; /usr/bin/cargoxx
+        # is a symlink to the in-store wrapper.
+        toArchPkg = drv:
+          let
+            pname = drv.pname or drv.name;
+            version = drv.version or "0";
+            mainProgram = drv.meta.mainProgram or pname;
+          in pkgs.runCommand "${pname}-${version}-1-x86_64.pkg.tar.zst" {
+            nativeBuildInputs = [ pkgs.libarchive pkgs.coreutils ];
+            closureInfo = pkgs.closureInfo { rootPaths = [ drv ]; };
+          } ''
+            stage=$(mktemp -d)
+            mkdir -p $stage/nix/store $stage/usr/bin
+            for p in $(cat $closureInfo/store-paths); do
+              cp -a "$p" $stage/nix/store/
+            done
+            ln -s ${drv}/bin/${mainProgram} $stage/usr/bin/${mainProgram}
+            installed_size=$(du -sk $stage | cut -f1)
+            cat > $stage/.PKGINFO <<EOF
+            pkgname = ${pname}
+            pkgver = ${version}-1
+            pkgdesc = ${drv.meta.description or pname}
+            builddate = 0
+            packager = nix-build
+            size = $installed_size
+            arch = x86_64
+            EOF
+            ( cd $stage && bsdtar --zstd -cf $out .PKGINFO nix usr )
+          '';
       in {
         packages.default = cargoxx-bin;
+        packages.appimage = bundlers-sys.toAppImage cargoxx-bin;
+        packages.dockerImage = bundlers-sys.toDockerImage cargoxx-bin;
+        packages.deb = bundlers-sys.toDEB cargoxx-bin;
+        packages.rpm = bundlers-sys.toRPM cargoxx-bin;
+        packages.archpkg = toArchPkg cargoxx-bin;
+
+        # Reusable packaging functions, all of the shape `drv -> drv`.
+        # Mirror the `to*` naming used by github:NixOS/bundlers.
+        lib.toAppImage = bundlers-sys.toAppImage;
+        lib.toDockerImage = bundlers-sys.toDockerImage;
+        lib.toDEB = bundlers-sys.toDEB;
+        lib.toRPM = bundlers-sys.toRPM;
+        lib.toArchPkg = toArchPkg;
         lib.buildCppPackage = buildCppPackage;
         devShells.default = pkgs.gcc15Stdenv.mkDerivation {
           name = "cargoxx-dev";