limit systems to the common ones in flake

flake.nix

@@ -11,9 +11,15 @@
       nixpkgs,
     }:
     let
+      supported-systems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "aarch64-darwin"
+        "x86_64-darwin"
+      ];
       forAllSystems =
         f:
-        nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed (
+        nixpkgs.lib.genAttrs supported-systems (
           system:
           f rec {
             inherit system;
@@ -55,7 +61,7 @@
               buildPhase = ''
                 mkdir -p public
                 hugo --baseURL=https://${domain}/
-                
+
                 python3 ./tools/merge_cals.py
                 upcoming="$(python3 tools/gen_upcoming.py static/all.ics 20 5 | tr '\n' ' ')"
                 cp static/all.ics public/all.ics