Add [[noreturn]] attributes to fix warning

	* libsupc++/nested_exception.h (__throw_with_nested_impl): Add
	noreturn attribute.

From-SVN: r255315

libstdc++-v3/ChangeLog

 2017-12-01  Jonathan Wakely  <jwakely@redhat.com>
 
+	* libsupc++/nested_exception.h (__throw_with_nested_impl): Add
+	noreturn attribute.
+
 	* include/bits/regex_executor.tcc (_Executor::_M_rep_once_more):
 	Remove semi-colon after function body.
 	* include/bits/uniform_int_dist.h (_Power_of_2): Likewise.

libstdc++-v3/libsupc++/nested_exception.h

@@ -92,6 +92,7 @@ namespace std
   // Throw an exception of unspecified type that is publicly derived from
   // both remove_reference_t<_Tp> and nested_exception.
   template<typename _Tp>
+    [[noreturn]]
     inline void
     __throw_with_nested_impl(_Tp&& __t, true_type)
     {
@@ -100,6 +101,7 @@ namespace std
     }
 
   template<typename _Tp>
+    [[noreturn]]
     inline void
     __throw_with_nested_impl(_Tp&& __t, false_type)
     { throw std::forward<_Tp>(__t); }