Index: test/lit.cfg
===================================================================
--- test/lit.cfg	(revision 187276)
+++ test/lit.cfg	(working copy)
@@ -211,11 +211,13 @@
 if cxx_under_test is None:
     cxx_under_test = getattr(config, 'cxx_under_test', None)
 
+if cxx_under_test is None:
     # If no specific cxx_under_test was given, attempt to infer it as clang++.
     clangxx = lit.util.which('clang++', config.environment['PATH'])
     if clangxx is not None:
         cxx_under_test = clangxx
         lit.note("inferred cxx_under_test as: %r" % (cxx_under_test,))
+
 if cxx_under_test is None:
     lit.fatal('must specify user parameter cxx_under_test '
               '(e.g., --param=cxx_under_test=clang++)')