libxnd, pythonPackages.xnd: unstable-2018-11-27 -> unstable-2019-08-01

this is the most recent commit to upstream's master at time of writing

includes fixes of python package for darwin

pkgs/development/python-modules/xnd/default.nix

@@ -1,4 +1,6 @@
-{ buildPythonPackage
+{ stdenv
+, buildPythonPackage
+, python
 , ndtypes
 , libndtypes
 , libxnd
@@ -25,5 +27,14 @@ buildPythonPackage {
   postInstall = ''
     mkdir $out/include
     cp python/xnd/*.h $out/include
+  '' + stdenv.lib.optionalString stdenv.isDarwin ''
+    install_name_tool -add_rpath ${libxnd}/lib $out/${python.sitePackages}/xnd/_xnd.*.so
+  '';
+
+  checkPhase = ''
+    pushd python
+    mv xnd _xnd
+    python test_xnd.py
+    popd
   '';
 }