netbsd.install: fix build with new Darwin SDK

To avoid adding headers to the SDK it does not have normally
(`libutil.h`), darwin.libutil is not propagated. It must be included as
a build input when it is needed by packages.

pkgs/os-specific/bsd/netbsd/pkgs/install/package.nix

@@ -1,4 +1,5 @@
 {
+  lib,
   mkDerivation,
   writeShellScript,
   mtree,
@@ -10,7 +11,8 @@
   groff,
   compatIfNeeded,
   fts,
-
+  darwin,
+  stdenv,
 }:
 
 # HACK: to ensure parent directories exist. This emulates GNU
@@ -42,7 +44,8 @@ mkDerivation {
     # fts header is needed. glibc already has this header, but musl doesn't,
     # so make sure pkgsMusl.netbsd.install still builds in case you want to
     # remove it!
-    ++ [ fts ];
+    ++ [ fts ]
+    ++ lib.optionals stdenv.hostPlatform.isDarwin [ darwin.libutil ];
   installPhase = ''
     runHook preInstall