docker runner assumes root

My container was built to start with a non root user instead of root. However the runner wants to access /builds in the container and the container's user doesn't have access. Not sure what to do as I don't want to rebuild my image with root access only.

[[runners]]
  name = "puppet38"
  url = "https://ci.gitlab.com/"
  token = "supersecrettoken"
  limit = 0
  executor = "docker"
  [runners.docker]
    image = "logicminds/centos-puppetdev:latest3.8.x"
    privileged = false
    volumes = ["/cache"]

gitlab-ci-multi-runner 0.4.2 (1e86428)
Using Docker executor with image logicminds/centos-puppetdev:latest3.8.x ...
mkdir: cannot create directory '/builds/logicminds/profiles': Permission denied
bash: line 5: /builds/logicminds/profiles.sh: Permission denied

Build failed with exit code 1