refactor: packages & fhs

modules/nixos/desktop/fhs.nix

@@ -0,0 +1,19 @@
+{pkgs, ...}: {
+  # FHS environment, flatpak, appImage, etc.
+  environment.systemPackages = [
+    # create a fhs environment by command `fhs`, so we can run non-nixos packages in nixos!
+    (
+      let
+        base = pkgs.appimageTools.defaultFhsEnvArgs;
+      in
+        pkgs.buildFHSUserEnv (base
+          // {
+            name = "fhs";
+            targetPkgs = pkgs: (base.targetPkgs pkgs) ++ [pkgs.pkg-config];
+            profile = "export FHS=1";
+            runScript = "bash";
+            extraOutputsToInstall = ["dev"];
+          })
+    )
+  ];
+}