Merge pull request swiftlang#63349 from aschwaighofer/fix_anyhashable_rpwt

Fix AnyHashableSupport.cpp for SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES

Author: swift-ci

stdlib/public/runtime/AnyHashableSupport.cpp

@@ -98,7 +98,12 @@ findHashableBaseTypeImpl(const Metadata *type) {
     return nullptr;
   }
   // By this point, `type` is known to conform to `Hashable`.
+#if SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES
+  const auto *conformance = reinterpret_cast<const RelativeWitnessTable*>(
+    witnessTable)->getDescription();
+#else
   const auto *conformance = witnessTable->getDescription();
+#endif
   const Metadata *baseTypeThatConformsToHashable =
     findConformingSuperclass(type, conformance);
   HashableConformanceKey key{type};