refactor: group build-machine-related config into one "role" file

hosts/by-name/desko/default.nix

@@ -4,11 +4,11 @@
     ./fs.nix
   ];
 
+  sane.roles.build-machine = true;
   sane.roles.client = true;
   sane.services.wg-home.enable = true;
   sane.services.wg-home.ip = config.sane.hosts.by-name."desko".wg-home.ip;
   sane.services.duplicity.enable = true;
-  sane.services.nixserve.enable = true;
   sane.services.nixserve.sopsFile = ../../../secrets/desko.yaml;
   sane.persist.enable = true;
 

hosts/by-name/servo/default.nix

@@ -15,6 +15,7 @@
     signaldctl.enableFor.user.colin = true;
   };
 
+  sane.roles.build-machine = true;
   sane.persist.enable = true;
   sane.services.dyn-dns.enable = true;
   sane.services.wg-home.enable = true;

hosts/modules/hardware/x86_64.nix

@@ -9,11 +9,6 @@
       # efi_pstore evivars
     ];
 
-    # enable cross compilation
-    boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
-    # nixpkgs.config.allowUnsupportedSystem = true;
-    # nixpkgs.crossSystem.system = "aarch64-linux";
-
     powerManagement.cpuFreqGovernor = "powersave";
     hardware.cpu.amd.updateMicrocode = true;    # desktop
     hardware.cpu.intel.updateMicrocode = true;  # laptop

hosts/modules/roles/build-machine.nix

@@ -0,0 +1,20 @@
+{ config, lib, ... }:
+
+let
+  inherit (lib) mkIf mkOption types;
+in
+{
+  options.sane.roles.build-machine = mkOption {
+    type = types.bool;
+    default = false;
+  };
+
+  config = mkIf config.sane.roles.build-machine {
+    # serve packages to other machines that ask for them
+    sane.services.nixserve.enable = true;
+
+    # enable cross compilation
+    boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
+    # nixpkgs.config.allowUnsupportedSystem = true;
+  };
+}

hosts/modules/roles/default.nix

@@ -1,6 +1,7 @@
 { ... }:
 {
   imports = [
+    ./build-machine.nix
     ./client
   ];
 }