Flutter in Docker container fails in Jenkins but not locally - docker

Question

I'm trying to get one of our very simple flutter apps to run its test suite in Jenkins.
I have the following Dockerfile:
FROM ubuntu:bionic
ARG WORKING_DIR=${HOME}
ARG FLUTTER_ARCHIVE=flutter_linux_v0.5.1-beta.tar.xz
COPY ${FLUTTER_ARCHIVE} ${WORKING_DIR}
RUN apt-get update
RUN apt-get -y install xz-utils
RUN tar -xf "${WORKING_DIR}/${FLUTTER_ARCHIVE}"
ENV PATH="${WORKING_DIR}/flutter/bin:${PATH}"
RUN apt-get -y install git libglu1 lib32stdc++6
RUN rm ${WORKING_DIR}/${FLUTTER_ARCHIVE}
I build the container on my machine, navigate to the source code directory of the flutter app and run the following command:
docker run -td -vpwd:/source flutter:flutter
Where flutter:flutter is my built image.
I navigate into the container using docker exec and execute flutter packages get and then flutter test. Everything works as expected and all tests pass.
However, when I try to use the exact same Dockerfile through Jenkins, I get following error:
/flutter/bin/flutter: line 161: /flutter/bin/cache/dart-sdk/bin/dart: Permission denied
I'm guessing it has something do with users and that differs somehow between how Jenkins runs and how it works when I run the steps manually. The steps in the Jenkinsfile are exactly as what I ran manually above:
stages {
stage('test') {
steps {
script {
sh 'flutter packages get'
sh 'flutter test'
}
}
}
}
And I have pointed to our local registry where the image resides:
agent {
docker "flutter:flutter"
}
I am out of ideas and I don't really know how to solve this error. Any help would be greatly appreciated.
UPDATE
I have tried the following:
Creating a user in the Dockerfile using useradd and then switching to that user using USER <user> Dockerfile syntax and performing all operations as that user.
Creating a user in the Dockerfile using useradd, performing all operations as root but then setting chown user:user -R /flutter to change ownership of Flutter directory
Both of the above required me to add the following to the Jenkinsfile:
agent {
docker {
image 'flutter:flutter'
args '-u user --privileged'
}
}
But still no luck.