我正在运行以下命令来创建docker映像，目的是在ubuntu上安装特定版本的Chromedriver，然后安装jenkins。但是，以下脚本仅安装jenkins，即使成功运行也未安装chromedriver。您能告诉我我在做什么错吗？
# See https://codeship.com/documentation/docker/browser-testing/
FROM ubuntu:xenial
RUN apt-get update && apt-get -qq -y install curl
# We need wget to set up the PPA and xvfb to have a virtual screen and unzip to install the Chromedriver
RUN apt-get install -y wget xvfb unzip
# Set up the Chrome PPA
RUN wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
RUN echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list
# Update the package list and install chrome
RUN apt-get update -y
RUN apt-get install -y google-chrome-stable
# Set up Chromedriver Environment variables
ENV CHROMEDRIVER_VERSION 76.0.3809.12
ENV CHROMEDRIVER_DIR /chromedriver
RUN mkdir $CHROMEDRIVER_DIR
# Download and install Chromedriver
RUN wget -q --continue -P $CHROMEDRIVER_DIR "http://chromedriver.storage.googleapis.com/$CHROMEDRIVER_VERSION/chromedriver_linux64.zip"
RUN unzip $CHROMEDRIVER_DIR/chromedriver* -d $CHROMEDRIVER_DIR
# Put Chromedriver into the PATH
ENV PATH $CHROMEDRIVER_DIR:$PATH
# FROM jenkins/jenkins:2.176.3
FROM jenkins/jenkins
USER root
ENV TZ=Europe/Berlin
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
USER jenkins