[lit] Fix running tests that require 'examples'.

Differential Revision: https://reviews.llvm.org/D46514
Patch by Nikolai Kosjar.

llvm-svn: 331786
diff --git a/clang/test/lit.cfg.py b/clang/test/lit.cfg.py
index 5323cfe..a812cd1 100644
--- a/clang/test/lit.cfg.py
+++ b/clang/test/lit.cfg.py
@@ -63,6 +63,7 @@
 ]
 
 if config.clang_examples:
+    config.available_features.add('examples')
     tools.append('clang-interpreter')
 
 llvm_config.add_tool_substitutions(tools, tool_dirs)