nixos/nix-channel: substitute getent path in preSwitchCheck (#527769)

nixos/modules/config/nix-channel.nix

@@ -6,7 +6,12 @@
   - ./nix.nix
   - ./nix-flakes.nix
 */
-{ config, lib, ... }:
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
 let
   inherit (lib)
     mkIf
@@ -98,7 +103,9 @@ in
     ];
 
     system.preSwitchChecks.no-nix-channel = mkIf (!cfg.channel.enable) (
-      builtins.readFile ./nix-channel/pre-switch-check.sh
+      lib.replaceStrings [ "@getent@" ] [ (lib.getExe pkgs.getent) ] (
+        builtins.readFile ./nix-channel/pre-switch-check.sh
+      )
     );
   };
 }

nixos/modules/config/nix-channel/pre-switch-check.sh

@@ -16,7 +16,7 @@ while IFS=: read -r _ _ _ _ _ home _ ; do
         warn "$home/.nix-defexpr/channels exists, but channels have been disabled."
         explainChannelWarning=1
     fi
-done < <(getent passwd)
+done < <(@getent@ passwd)
 if [[ $explainChannelWarning -eq 1 ]]; then
     echo "Due to https://github.com/NixOS/nix/issues/9574, Nix may still use these channels when NIX_PATH is unset." >&2
     echo "Delete the above directory or directories to prevent this." >&2