Protect std::ostream::sentry test under libcpp-no-exceptions

[rogfer01]

Summary

Skip test that throws an exception.

[mclow.lists]

LGTM

test/std/input.output/iostream.format/output.streams/ostream_sentry/destruct.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: libcpp-no-exceptions
 // <ostream>
 
 // template <class charT, class traits = char_traits<charT> >
 // class basic_ostream::sentry;
 
 // ~sentry();
 
 #include <ostream>
 #include <cassert>
 
+#include "test_macros.h"
+
 int sync_called = 0;
 
 template <class CharT>
 struct testbuf1
     : public std::basic_streambuf<CharT>
 {
     testbuf1() {}
 
int main()
     {
         testbuf1<char> sb;
         std::ostream os(&sb);
         std::ostream::sentry s(os);
         assert(bool(s));
         unitbuf(os);
     }
     assert(sync_called == 1);
+#ifndef TEST_HAS_NO_EXCEPTIONS
     {
         testbuf1<char> sb;
         std::ostream os(&sb);
         try
         {
             std::ostream::sentry s(os);
             assert(bool(s));
             unitbuf(os);
             throw 1;
         }
         catch (...)
         {
         }
         assert(sync_called == 1);
     }
+#endif
 }