gnustep: attempt to fix osx building

Set with-layout=fhs. This should prevent OS X from having compat issues.

pkgs/desktops/gnustep/make/default.nix

···
 { stdenv, fetchurl, clang, which, libobjc }:
+
 let
   version = "2.6.8";
 in
+
 stdenv.mkDerivation rec {
   name = "gnustep-make-${version}";
+
   src = fetchurl {
     url = "ftp://ftp.gnustep.org/pub/gnustep/core/gnustep-make-${version}.tar.gz";
     sha256 = "0r00439f7vrggdwv60n8p626gnyymhq968i5x9ad2i4v6g8x4gk0";
   };
-  configureFlags = "--with-installation-domain=SYSTEM";
+
+  configureFlags = [
+    "--with-layout=fhs-system"
+    "--disable-install-p"
+  ];
+
+  preConfigure = ''
+    configureFlags="$configureFlags --with-config-file=$out/etc/GNUstep/GNUstep.conf"
+  '';
+
+  makeFlags = [
+    "GNUSTEP_INSTALLATION_DOMAIN=SYSTEM"
+  ];
+
   buildInputs = [ clang which libobjc ];
   patches = [ ./fixup-paths.patch ];
   setupHook = ./setup-hook.sh;
   meta = {
     description = "A build manager for GNUstep";
-
     homepage = http://gnustep.org/;
-
     license = stdenv.lib.licenses.lgpl2Plus;
-
     maintainers = with stdenv.lib.maintainers; [ ashalkhakov matthewbauer ];
-    platforms = stdenv.lib.platforms.linux;
+    platforms = stdenv.lib.platforms.unix;
   };
 }