Zhang Xiongpang: Add definitions for const data members. Fixes http://llvm.org/bugs/show_bug.cgi?id=14585.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@170026 91177308-0d34-0410-b5e6-96231b3b80d8

test/utilities/time/time.clock/time.clock.system/consistency.pass.cpp

@@ -15,6 +15,9 @@
 
 #include <chrono>
 
+template <class _Tp>
+void test(const _Tp &) {}
+
 int main()
 {
     typedef std::chrono::system_clock C;
@@ -23,4 +26,5 @@ int main()
     static_assert((std::is_same<C::duration, C::time_point::duration>::value), "");
     static_assert((std::is_same<C::time_point::clock, C>::value), "");
     static_assert((C::is_steady || !C::is_steady), "");
+    test(std::chrono::system_clock::is_steady);
 }