writers: use callPackages to import sub-groups of writers

Use callPackages instead of plain import to get proper splicing. Without this,
writeNginxConfig fails when cross-compiling.

pkgs/build-support/writers/default.nix

···
-{ pkgs, config, lib }:
+{ config, lib, callPackages }:
 
 let
   aliases = if config.allowAliases then (import ./aliases.nix lib) else prev: {};
 
   # Writers for JSON-like data structures
-  dataWriters = import ./data.nix {
-    inherit lib; inherit (pkgs) runCommandNoCC dasel;
-  };
+  dataWriters = callPackages ./data.nix { };
 
   # Writers for scripts
-  scriptWriters = import ./scripts.nix {
-    inherit lib pkgs;
-  };
+  scriptWriters = callPackages ./scripts.nix { };
 
   writers = scriptWriters // dataWriters;
 in

pkgs/build-support/writers/scripts.nix

···
-{ pkgs, lib }:
+{ pkgs, buildPackages, lib, stdenv, libiconv, mkNugetDeps, mkNugetSource, gixy }:
 let
   inherit (lib)
     concatMapStringsSep
···
     stringLength
     strings
     types
-    ;
-
-  inherit (pkgs)
-    buildPackages
-    gixy
-    libiconv
-    mkNugetDeps
-    mkNugetSource
-    stdenv
     ;
 in
 rec {