Add support for environment.systemPackages.

nix/modules/default.nix

@@ -6,6 +6,7 @@
 }:
 {
   imports = [
+    ./environment.nix
     ./etc.nix
     ./systemd.nix
     ./upstream/nixpkgs
@@ -16,7 +17,6 @@
       inherit (lib) types;
     in
     {
-
       nixpkgs = {
         # TODO: switch to lib.systems.parsedPlatform
         hostPlatform = lib.mkOption {

nix/modules/environment.nix

@@ -0,0 +1,17 @@
+{ lib, config, pkgs, ... }:
+
+{
+  options.environment = {
+    systemPackages = lib.mkOption {
+      type = lib.types.listOf lib.types.package;
+      default = [ ];
+    };
+  };
+
+  config = {
+    environment.etc."profile.d/system-manager-path.sh".source =
+      pkgs.writeShellScript "system-manager-path.sh" ''
+        export PATH=${lib.makeBinPath config.environment.systemPackages}:''${PATH}
+      '';
+  };
+}