Revert "Revert "Merge to upstream r304942.""

This reverts commit 38a0d5af7e.

Test: make checkbuild
Test: ./run_tests.py
Test: ./run_tests.py --bitness 64

test/std/thread/thread.mutex/thread.lock.algorithm/lock.pass.cpp

@@ -188,7 +188,7 @@ int main()
         }
     }
 #endif
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#if TEST_STD_VER >= 11
     {
         L0 l0;
         L0 l1;
@@ -518,5 +518,5 @@ int main()
         }
     }
 #endif  // TEST_HAS_NO_EXCEPTIONS
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif // TEST_STD_VER >= 11
 }