writeShellApplication: fix meta.position

This avoids getting random pings when the trivial builders are changed.

pkgs/build-support/trivial-builders/default.nix

@@ -109,6 +109,7 @@ rec {
       allowSubstitutes ? false,
       preferLocalBuild ? true,
       derivationArgs ? { },
+      pos ? builtins.unsafeGetAttrPos "name" args,
     }@args:
     assert lib.assertMsg (destination != "" -> (lib.hasPrefix "/" destination && destination != "/")) ''
       destination must be an absolute path, relative to the derivation's out path,
@@ -123,8 +124,8 @@ rec {
     runCommand name
       (
         {
-          pos = builtins.unsafeGetAttrPos "name" args;
           inherit
+            pos
             text
             executable
             checkPhase
@@ -261,6 +262,7 @@ rec {
       inheritPath ? true,
     }@args:
     writeTextFile {
+      pos = builtins.unsafeGetAttrPos "name" args;
       inherit
         name
         meta