chore: add flake.nix for reproducible builds

Author: wjkoh

flake.lock

@@ -0,0 +1,57 @@
+{
+  description = "SQLite Vector Extension";
+
+  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 = nixpkgs.legacyPackages.${system};
+        stdenv = pkgs.stdenv;
+        version = "0.9.53";
+      in
+      {
+        packages.default = stdenv.mkDerivation {
+          pname = "sqlite-vector";
+          inherit version;
+
+          src = pkgs.lib.cleanSource ./.;
+
+          makeFlags = [
+            "CC=${stdenv.cc.targetPrefix}cc"
+          ] ++ pkgs.lib.optionals stdenv.isDarwin [
+            "ARCH=${if stdenv.hostPlatform.isAarch64 then "arm64" else "x86_64"}"
+          ];
+
+          installPhase = "install -D dist/vector* -t $out/lib";
+
+          checkInputs = [ pkgs.sqlite ];
+          doCheck = true;
+          checkPhase = ''
+            make test
+          '';
+        };
+
+        devShells.default =
+          let
+            sqlite-vector = self.packages.${system}.default;
+          in
+          pkgs.mkShell {
+            packages = [
+              pkgs.sqlite
+              pkgs.gnumake
+              sqlite-vector
+            ];
+
+            shellHook = ''
+              export SQLITE_VECTOR_LIB="${sqlite-vector}/lib/vector${stdenv.hostPlatform.extensions.sharedLibrary}"
+              echo "SQLite Vector extension available at: $SQLITE_VECTOR_LIB"
+              echo "Load it in sqlite3 with: .load $SQLITE_VECTOR_LIB"
+            '';
+          };
+      }
+    );
+}