fix: dockerfile cpu

docker/ubuntu18-cpu/Dockerfile

 FROM registry.baidubce.com/paddlepaddle/paddle:2.2.2
 LABEL maintainer="paddlesl@baidu.com"
 
+RUN apt-get update \
+  && apt-get install libsndfile-dev \
+  && apt-get clean \
+  && rm -rf /var/lib/apt/lists/*
+
 RUN git clone --depth 1 https://github.com/PaddlePaddle/PaddleSpeech.git /home/PaddleSpeech  
 RUN pip3 uninstall mccabe -y ; exit 0;
 RUN pip3 install multiprocess==0.70.12 importlib-metadata==4.2.0 dill==0.3.4
 
-RUN cd /home/PaddleSpeech/audio
-RUN python setup.py bdist_wheel
-
-RUN cd /home/PaddleSpeech
+WORKDIR /home/PaddleSpeech/
 RUN python setup.py bdist_wheel
-RUN pip install audio/dist/*.whl dist/*.whl
+RUN pip install dist/*.whl -i https://pypi.tuna.tsinghua.edu.cn/simple
 
-WORKDIR /home/PaddleSpeech/
+CMD ['bash']