Index: test/lit.cfg
===================================================================
--- test/lit.cfg
+++ test/lit.cfg
@@ -53,6 +53,11 @@
 
 config.test_exec_root = os.path.join(obj_root, 'test')
 
+# Check if we have produced a Clang with this build (in-tree)
+this_clang = os.path.join(obj_root, '../../bin/clang++')
+if os.path.exists(this_clang):
+    config.cxx_under_test = this_clang
+
 cfg_variant = getattr(config, 'configuration_variant', 'libcxxabi')
 if cfg_variant:
     print 'Using configuration variant: %s' % cfg_variant