PR libstdc++/81266 fix std::thread::native_handle_type test

The test uses remove_pointer because in most cases native_handle_type is
a pointer to the actual type that the C++ class contains. However, for
std::thread, native_handle_type is the same type as the type contained
in std::thread, and so remove_pointer is not needed. On targets where
pthread_t is a pointer type remove_pointer<native_handle_type> is not a
no-op, instead it transforms pthread_t and causes the test to fail.

The fix is to not apply remove_pointer when testing std::thread.

	PR libstdc++/81266
	* testsuite/util/thread/all.h: Do not use remove_pointer for
	std::thread::native_handle_type.

From-SVN: r271080

libstdc++-v3/ChangeLog

 2019-05-10  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/81266
+	* testsuite/util/thread/all.h: Do not use remove_pointer for
+	std::thread::native_handle_type.
+
 	PR libstdc++/90397
 	* include/std/variant (_Variant_storage<false, Types...>::_M_storage())
 	(_Variant_storage<true, Types...>::_M_reset()))

libstdc++-v3/testsuite/util/thread/all.h

@@ -25,6 +25,7 @@
 #include <sstream>
 #include <stdexcept>
 #include <type_traits>
+#include <thread>
 
 // C++11 only.
 namespace __gnu_test
@@ -39,7 +40,12 @@ namespace __gnu_test
 
       // Remove possible pointer type.
       typedef typename test_type::native_handle_type native_handle;
-      typedef typename std::remove_pointer<native_handle>::type native_type;
+      // For std::thread native_handle_type is the type of its data member,
+      // for other types it's a pointer to the type of the data member.
+      typedef typename std::conditional<
+	std::is_same<test_type, std::thread>::value,
+	native_handle,
+	typename std::remove_pointer<native_handle>::type>::type native_type;
 
       int st = sizeof(test_type);
       int snt = sizeof(native_type);