Fix build of tests with libstdc++-16

libstdc++-16 provides std::hash<__int128> also in strict (-std=c++17) mode
--- a/test/rocprim/test_device_segmented_topk.cpp
+++ b/test/rocprim/test_device_segmented_topk.cpp
@@ -91,6 +91,9 @@ void inline compare_k(InputVector input, OutputVector output, SizeOut k)
 
 namespace std
 {
+// provided by libstdc++ (GNU mode, or since 16 also strict mode) and libc++
+#if !defined(__GLIBCXX_TYPE_INT_N_0) && !(defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE >= 16) \
+    && !defined(_LIBCPP_VERSION)
 template<>
 struct hash<rocprim::int128_t>
 {
@@ -113,6 +116,7 @@ struct hash<rocprim::uint128_t>
         return (hash<std::uint64_t>{}(low) * 31) + hash<std::uint64_t>{}(high);
     }
 };
+#endif
 
 template<>
 struct hash<rocprim::half>