Documentation: use a :doc: link instead of an absolute http:// link.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168286 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/TestingGuide.rst b/docs/TestingGuide.rst
index ad78d0f..69d2422 100644
--- a/docs/TestingGuide.rst
+++ b/docs/TestingGuide.rst
@@ -206,8 +206,8 @@
 you're adding a directory of tests, just copy ``lit.local.cfg`` from
 another directory to get running. The standard ``lit.local.cfg`` simply
 specifies which files to look in for tests. Any directory that contains
-only directories does not need the ``lit.local.cfg`` file. Read the `Lit
-documentation <http://llvm.org/cmds/lit.html>`_ for more information.
+only directories does not need the ``lit.local.cfg`` file. Read the :doc:`Lit
+documentation <CommandGuide/lit>` for more information.
 
 The ``llvm-runtests`` function looks at each file that is passed to it
 and gathers any lines together that match "RUN:". These are the "RUN"