core: Fix clang build

Recent changes to the build system that made more warnings be flagged as
errors caused building via clang to break.

Fixes #4795

src/core/hle/kernel/handle_table.cpp

@@ -68,7 +68,7 @@ ResultVal<Handle> HandleTable::Create(std::shared_ptr<Object> obj) {
     generations[slot] = generation;
     objects[slot] = std::move(obj);
 
-    Handle handle = generation | (slot << 15);
+    const auto handle = static_cast<Handle>(generation | static_cast<u16>(slot << 15));
     return MakeResult<Handle>(handle);
 }