Add nix.shell

.envrc

@@ -0,0 +1,4 @@
+# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+# Exceptions. See /LICENSE for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+use nix

.gitignore

@@ -43,3 +43,6 @@
 
 # Ignore the .gdb_history that's created next to the project-specific .gdbinit
 .gdb_history
+
+#Ignore direnv directory
+/.direnv

shell.nix

@@ -0,0 +1,29 @@
+# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+# Exceptions. See /LICENSE for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+{pkgs ? import <nixpkgs> {}}:
+let
+  llvmPackages = pkgs.llvmPackages_19;
+in
+  pkgs.mkShell.override { stdenv = llvmPackages.libcxxStdenv; } {
+    packages = [
+      pkgs.python3
+      pkgs.bazel_7
+      llvmPackages.clangUseLLVM
+      llvmPackages.libcxx
+      llvmPackages.libunwind
+      llvmPackages.llvm
+      llvmPackages.bintools
+    ];
+
+    buildInputs = [
+    ];
+    nativeBuildInputs = [
+    ];
+
+    NIX_LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [
+      pkgs.stdenv.cc.cc
+      pkgs.libz
+    ];
+    NIX_LD = pkgs.lib.fileContents "${pkgs.stdenv.cc}/nix-support/dynamic-linker";
+  }