Function start_executing_work 

fn start_executing_work<B: ExtraBackendMethods>(
    backend: B,
    tcx: TyCtxt<'_>,
    crate_info: &CrateInfo,
    shared_emitter: SharedEmitter,
    codegen_worker_send: Sender<CguMessage>,
    coordinator_receive: Receiver<Message<B>>,
    regular_config: Arc<ModuleConfig>,
    allocator_config: Arc<ModuleConfig>,
    allocator_module: Option<ModuleCodegen<B::Module>>,
    tx_to_llvm_workers: Sender<Message<B>>,
) -> JoinHandle<Result<CompiledModules, ()>>