Add noexcept(false) to more strongly indicate that not being noexcept is important for hash tests.

llvm-svn: 299735
diff --git a/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp b/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp
index 6d9a260..4a0bf6d 100644
--- a/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp
@@ -26,7 +26,7 @@
 
 template <>
 struct hash<B> {
-  size_t operator()(B const&) { return 0; }
+  size_t operator()(B const&) noexcept(false) { return 0; }
 };
 
 }