feat: add flake.nix for nixOS development

.envrc

@@ -0,0 +1,5 @@
+strict_env
+watch_file ./*.nix
+use flake
+layout python
+

flake.nix

@@ -0,0 +1,70 @@
+{
+  description = "INGP dev env";
+
+  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 = import nixpkgs {
+          inherit system;
+          config = {
+            allowUnfree = true;
+            cudaSupport = true;
+            config.cudaVersion = "12";
+          };
+        };
+      in
+      {
+        devShell = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            gcc
+            gdb
+            cmake
+            pkg-config
+            binutils
+            zlib
+
+            xorg.libX11.dev
+            xorg.libXi.dev
+            xorg.libXrandr.dev
+            xorg.libXinerama.dev
+            xorg.libXcursor.dev
+            xorg.libXext.dev
+            xorg.libXfixes.dev
+            xorg.libXrender.dev
+            libGL
+            glew
+
+            vulkan-loader
+            vulkan-headers
+            vulkan-validation-layers
+            vulkan-extension-layer
+            vulkan-tools
+
+            python3
+            stdenv.cc.cc.lib
+
+            cudatoolkit
+            cudaPackages.cuda_cudart
+            cudaPackages.cuda_nvrtc
+            cudaPackages.cuda_nvtx
+          ];
+
+          shellHook = ''
+            export CUDA_PATH="${pkgs.cudatoolkit}"
+            export CLANGD_CUDA_INCLUDE="${pkgs.cudatoolkit}"
+
+            export LD_LIBRARY_PATH="/run/opengl-driver/lib:${pkgs.zlib}/lib:${pkgs.stdenv.cc.cc.lib}/lib:''${LD_LIBRARY_PATH:-}"
+            export VULKAN_SDK="${pkgs.vulkan-loader}"
+
+            export VK_LAYER_PATH="${pkgs.vulkan-validation-layers}/share/vulkan/explicit_layer.d:${pkgs.vulkan-extension-layer}/share/vulkan/explicit_layer.d"
+            export VK_ICD_FILENAMES="/run/opengl-driver/share/vulkan/icd.d/nvidia_icd.x86_64.json"
+          '';
+        };
+      }
+    );
+}