Method start

compiler/test/kernel/common/timer.h:18–23

        m_stopped = false;
    }
    void start() {
        mgb_assert(!m_started);
        mgb_assert(!m_stopped);
        m_started = true;
        m_start_point = clock::now();
    }
    void stop() {
        mgb_assert(m_started);
        mgb_assert(!m_stopped);