[lldb] Add missing wasm switch case

TypeSystemClang.cpp:4855:13: error: enumeration value 'WasmExternRef' not handled in switch [-Werror,-Wswitch]

Author: d0k

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

@@ -5118,6 +5118,10 @@ lldb::Encoding TypeSystemClang::GetEncoding(lldb::opaque_compiler_type_t type,
     case clang::BuiltinType::RvvBool64:
       break;
 
+    // WebAssembly builtin types.
+    case clang::BuiltinType::WasmExternRef:
+      break;
+
     case clang::BuiltinType::IncompleteMatrixIdx:
       break;
     }