disable community cachix on macos

ssl at work prevents connection

modules/common/default.nix

@@ -88,8 +88,9 @@
       settings = {
 
         # Add community Cachix to binary cache
-        substituters = [ "https://nix-community.cachix.org" ];
-        trusted-public-keys = [
+        substituters = lib.mkIf (!pkgs.stdenv.isDarwin)
+          [ "https://nix-community.cachix.org" ];
+        trusted-public-keys = lib.mkIf (!pkgs.stdenv.isDarwin) [
           "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
         ];