feat(flake): add Nix development shell (#1592)

* feat(build): add simple nix flake with formatter for nix code

* feat(flake): setup rust toolchain, able to build and run unit tests

* feat(flake): add support for arm linux and macos

* feat(toolchain): add rust-src and rust-analyzer to the toolchain

flake.lock

@@ -0,0 +1,103 @@
+{
+  "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"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1779560665,
+        "narHash": "sha256-tpyBcxPpcQb8ukyNF7DoCwfSY3VPsxHoYwj00Cayv5o=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "64c08a7ca051951c8eae34e3e3cb1e202fe36786",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay",
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1779851998,
+        "narHash": "sha256-UkkMh3bX9QW4Luqkm98nUaOqKWrU6i65mUnph3WeSSw=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "6cddd512fa2bf7231f098d3a2f92f6e4cff71e0a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1775636079,
+        "narHash": "sha256-pc20NRoMdiar8oPQceQT47UUZMBTiMdUuWrYu2obUP0=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "790751ff7fd3801feeaf96d7dc416a8d581265ba",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,61 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+{
+  description = "OpenShell development environment";
+
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    treefmt-nix = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs =
+    {
+      flake-utils,
+      nixpkgs,
+      rust-overlay,
+      treefmt-nix,
+      ...
+    }:
+    flake-utils.lib.eachSystem [ "x86_64-linux" "aarch64-linux" "aarch64-darwin" ] (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ (import rust-overlay) ];
+        };
+        rustToolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+        treefmtEval = treefmt-nix.lib.evalModule pkgs {
+          projectRootFile = "flake.nix";
+          programs.nixfmt.enable = true;
+        };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            rustToolchain
+            # Required to find packages
+            pkg-config
+            # Required for bindgen generation.
+            llvmPackages.libclang
+            # system dependency for openshell-prover
+            z3
+          ];
+
+          env = {
+            LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";
+          };
+        };
+
+        formatter = treefmtEval.config.build.wrapper;
+      }
+    );
+}

rust-toolchain.toml

@@ -3,3 +3,4 @@
 
 [toolchain]
 channel = "1.95.0"
+components = [ "rustfmt", "rust-src", "rust-analyzer" ]