node-packages: use util-linux instead of utillinux in node-env.nix

The `util-linux` alias to `utillinux` has been replaced by a `throw` in
commit a9e1f4e. The check must be
reversed.

Also, tidy things up by using the `util-linux` variable name instead of
the older `utillinux`.

Author: samueltardieu

pkgs/development/node-packages/node-env.nix

@@ -4,7 +4,7 @@
 
 let
   # Workaround to cope with utillinux in Nixpkgs 20.09 and util-linux in Nixpkgs master
-  utillinux = if pkgs ? utillinux then pkgs.utillinux else pkgs.util-linux;
+  util-linux = if pkgs ? util-linux then pkgs.util-linux else pkgs.utillinux;
 
   python = if nodejs ? python then nodejs.python else python2;
 
@@ -499,7 +499,7 @@ let
     stdenv.mkDerivation ({
       name = "${name}${if version == null then "" else "-${version}"}";
       buildInputs = [ tarWrapper python nodejs ]
-        ++ lib.optional (stdenv.hostPlatform.isLinux) utillinux
+        ++ lib.optional (stdenv.hostPlatform.isLinux) util-linux
         ++ lib.optional (stdenv.hostPlatform.isDarwin) libtool
         ++ buildInputs;
 
@@ -591,7 +591,7 @@ let
         name = "node-dependencies-${name}${if version == null then "" else "-${version}"}";
 
         buildInputs = [ tarWrapper python nodejs ]
-          ++ lib.optional (stdenv.hostPlatform.isLinux) utillinux
+          ++ lib.optional (stdenv.hostPlatform.isLinux) util-linux
           ++ lib.optional (stdenv.hostPlatform.isDarwin) libtool
           ++ buildInputs;
 
@@ -662,7 +662,7 @@ let
     stdenv.mkDerivation ({
       name = "node-shell-${name}${if version == null then "" else "-${version}"}";
 
-      buildInputs = [ python nodejs ] ++ lib.optional (stdenv.hostPlatform.isLinux) utillinux ++ buildInputs;
+      buildInputs = [ python nodejs ] ++ lib.optional (stdenv.hostPlatform.isLinux) util-linux ++ buildInputs;
       buildCommand = ''
         mkdir -p $out/bin
         cat > $out/bin/shell <<EOF