Add nix build output and justfile

Add packages.default flake output that builds the lean-libclang binary
via nix build. Add justfile with build, run, nix-run, and clean recipes.
Add 'result' to .gitignore.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -1 +1,2 @@
 /.lake
+result

flake.nix

@@ -11,6 +11,40 @@
       supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
       forAllSystems = f: nixpkgs.lib.genAttrs supportedSystems f;
     in {
+      packages = forAllSystems (system:
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+            overlays = [ (lean4-nix.readToolchainFile ./lean-toolchain) ];
+          };
+          libclang = pkgs.llvmPackages.libclang;
+        in {
+          default = pkgs.stdenv.mkDerivation {
+            pname = "lean-libclang";
+            version = "0.1.0";
+            src = self;
+            nativeBuildInputs = [
+              pkgs.lean.lean-all
+              pkgs.llvmPackages.clang
+            ];
+            buildInputs = [
+              libclang.dev
+              libclang.lib
+            ];
+            env = {
+              LEAN_CC = "${pkgs.llvmPackages.clang}/bin/clang";
+            };
+            buildPhase = ''
+              export HOME=$(mktemp -d)
+              lake build
+            '';
+            installPhase = ''
+              mkdir -p $out/bin
+              cp .lake/build/bin/lean-libclang $out/bin/
+            '';
+          };
+        });
+
       devShells = forAllSystems (system:
         let
           pkgs = import nixpkgs {

justfile

@@ -0,0 +1,18 @@
+_default:
+    @just --list
+
+
+build:
+    nix develop --command lake build
+
+# Run the AST printer on a C file
+run file:
+    nix develop --command .lake/build/bin/lean-libclang {{file}}
+
+# Build and run via nix
+nix-run file:
+    nix run . -- {{file}}
+
+# Clean build artifacts
+clean:
+    nix develop --command lake clean