Update dependencies; support macOS

flake.nix

@@ -2,11 +2,19 @@
   outputs = {
     self,
     nixpkgs,
+    systems,
   }: let
-    sys = "x86_64-linux";
-    pkgs = nixpkgs.legacyPackages.${sys};
+    eachSystem = f:
+      nixpkgs.lib.genAttrs (import systems) (sys:
+        f {
+          inherit sys;
+          pkgs = nixpkgs.legacyPackages.${sys};
+        });
   in {
-    packages.${sys} = rec {
+    packages = eachSystem ({
+      sys,
+      pkgs,
+    }: rec {
       python3 = pkgs.python3.override {
         packageOverrides = final: prev: {
           milc = prev.milc.overrideAttrs {
@@ -35,16 +43,21 @@
       };
 
       qmk = pkgs.qmk.override {inherit python3;};
-    };
-    devShells.${sys}.default = pkgs.mkShell {
-      packages = with pkgs; [
-        self.packages.${sys}.qmk
-        clang
-        clang-tools
-      ];
-      shellHook = ''
-        export QMK_HOME=$PWD/qmk_firmware
-      '';
-    };
+    });
+    devShells = eachSystem ({
+      sys,
+      pkgs,
+    }: {
+      default = pkgs.mkShell {
+        packages = with pkgs; [
+          self.packages.${sys}.qmk
+          clang
+          clang-tools
+        ];
+        shellHook = ''
+          export QMK_HOME=$PWD/qmk_firmware
+        '';
+      };
+    });
   };
 }