exclude darwin to fix `nix flake check`

flake.nix

@@ -2,7 +2,11 @@
   inputs.flake-utils.url = "github:numtide/flake-utils";
 
   outputs = { self, nixpkgs, flake-utils }:
-    flake-utils.lib.eachDefaultSystem (system:
+    # don't include darwin because some packages are broken for darwin
+    # and we would like to use `nix flake check` (and packages that are
+    # marked broken will abort before it does checks for the other archs)
+    let systems = [ "aarch64-linux" "x86_64-linux" ]; in
+    flake-utils.lib.eachSystem systems (system:
       let pkgs = nixpkgs.legacyPackages.${system}; prev = pkgs; in
       {
         # see https://discourse.nixos.org/t/add-python-package-via-overlay/19783/4
@@ -74,7 +78,7 @@
               openscad
               xorg.xorgserver
               xvfb-run
-              blender
+              (if blender.meta.unsupported then null else blender)
               git
               imagemagick
               librsvg