dlib: 19.4 -> 19.6

pkgs/development/libraries/dlib/default.nix

@@ -1,18 +1,25 @@
-{ stdenv, fetchFromGitHub, cmake, xlibsWrapper }:
+{ stdenv, lib, fetchFromGitHub, cmake, pkgconfig, openblas, libpng, libjpeg
+, guiSupport ? false, libX11
+}:
 
 stdenv.mkDerivation rec {
-  version = "19.4";
+  version = "19.6";
   name = "dlib-${version}";
 
   src = fetchFromGitHub {
     owner = "davisking";
     repo = "dlib";
     rev ="v${version}";
-    sha256 = "0zqa36i4s5i7n6284sp22qrhm3k37n9vqmpz068nm02vj9h0a2j4";
+    sha256 = "1nlx4z53jnk7wysaxrzbyyqb65m45rw4g1fagazl2jvwh1qn49ds";
   };
 
+  postPatch = ''
+    rm -rf dlib/external
+  '';
+
   enableParallelBuilding = true;
-  nativeBuildInputs = [ cmake ];
+  nativeBuildInputs = [ cmake pkgconfig ];
+  buildInputs = [ openblas libpng libjpeg ] ++ lib.optional guiSupport libX11;
 
   meta = with stdenv.lib; {
     description = "A general purpose cross-platform C++ machine learning library";