system/activation: mention deps attr in activationScripts example (#363915)

Author: misuzu

nixos/modules/system/activation/activation-script.nix

@@ -110,14 +110,19 @@ in
       default = {};
 
       example = literalExpression ''
-        { stdio.text =
-          '''
-            # Needed by some programs.
-            ln -sfn /proc/self/fd /dev/fd
-            ln -sfn /proc/self/fd/0 /dev/stdin
-            ln -sfn /proc/self/fd/1 /dev/stdout
-            ln -sfn /proc/self/fd/2 /dev/stderr
-          ''';
+        {
+          stdio = {
+            # Run after /dev has been mounted
+            deps = [ "specialfs" ];
+            text =
+              '''
+                # Needed by some programs.
+                ln -sfn /proc/self/fd /dev/fd
+                ln -sfn /proc/self/fd/0 /dev/stdin
+                ln -sfn /proc/self/fd/1 /dev/stdout
+                ln -sfn /proc/self/fd/2 /dev/stderr
+              ''';
+          };
         }
       '';