prefetch-npm-deps: add nix to PATH

Fixes "No such file or directory" error when running prefetch-npm-deps
in its default mode (print hashes, for update scripts etc),
in an environment that doesn't have a `nix` binary (for `nix hash`).

pkgs/build-support/node/fetch-npm-deps/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenvNoCC, rustPlatform, makeWrapper, Security, gnutar, gzip, testers, fetchurl, prefetch-npm-deps, fetchNpmDeps }:
+{ lib, stdenvNoCC, rustPlatform, makeWrapper, Security, gnutar, gzip, nix, testers, fetchurl, prefetch-npm-deps, fetchNpmDeps }:
 
 {
   prefetch-npm-deps = rustPlatform.buildRustPackage {
@@ -20,7 +20,7 @@
     buildInputs = lib.optional stdenvNoCC.isDarwin Security;
 
     postInstall = ''
-      wrapProgram "$out/bin/prefetch-npm-deps" --prefix PATH : ${lib.makeBinPath [ gnutar gzip ]}
+      wrapProgram "$out/bin/prefetch-npm-deps" --prefix PATH : ${lib.makeBinPath [ gnutar gzip nix ]}
     '';
 
     passthru.tests =