feat: add nix flake

.gitignore

@@ -110,3 +110,6 @@ compile_commands.json
 
 # VIA(L) json files that don't belong in QMK repo
 via*.json
+
+# direnv
+.direnv/

flake.nix

@@ -0,0 +1,43 @@
+{
+  description = "qmk dev flake";
+
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/c0e881852006b132236cbf0301bd1939bb50867e";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+  inputs.poetry2nix.url = "github:nix-community/poetry2nix/11c0df8e348c0f169cd73a2e3d63f65c92baf666";
+
+  outputs = inputs @ {
+    nixpkgs,
+    flake-utils,
+    ...
+  }:
+    flake-utils.lib.eachDefaultSystem (
+      system: let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            (final: prev: {
+              python3 = prev.python3.override {
+                packageOverrides = self: super: {
+                  tomlkit = super.tomlkit.overridePythonAttrs (old: rec {
+                    version = "0.11.4";
+                    src = super.fetchPypi {
+                      inherit (old) pname;
+                      inherit version;
+                      sha256 = "sha256-MjWpAQ+uVDI+cnw6wG+3IHUv5mNbNCbjedrsYPvUSoM=";
+                    };
+                  });
+                };
+              };
+            })
+          ];
+        };
+        poetry2nix = import inputs.poetry2nix {
+          inherit pkgs;
+        };
+      in {
+        devShell = import ./shell.nix {
+          inherit pkgs poetry2nix;
+        };
+      }
+    );
+}

shell.nix

@@ -73,7 +73,7 @@ in
           [clang-tools dfu-programmer dfu-util diffutils git pythonEnv niv]
           ++ lib.optional avr [
             pkgsCross.avr.buildPackages.binutils
-            pkgsCross.avr.buildPackages.gcc
+            pkgsCross.avr.buildPackages.gcc8
             avrlibc
             avrdude
           ]