Index: lit.cfg
===================================================================
--- lit.cfg
+++ lit.cfg
@@ -351,6 +351,12 @@
             self.config.available_features.add(
                 'with_system_lib=%s' % sanitized_triple)
 
+        if 'libcpp-has-no-threads' in self.config.available_features:
+            self.compile_flags += ['-D_LIBCPP_HAS_NO_THREADS']
+
+        if 'no-monotonic-clock' in self.config.available_features:
+            self.compile_flags += ['-D_LIBCPP_HAS_NO_MONOTONIC_CLOCK']
+
     def configure_compile_flags(self):
         # Configure extra compiler flags.
         self.compile_flags += ['-I' + self.src_root + '/include',