Plugin is relying on Docker for container management.
Remoting is established with a fixed image jenkinsci/slave.
To prevent classes version mismatch, we use docker cp at startup to inject the remoting jar bundled with Jenkins into the
container.
TMPDIR and java.io.tmpdir are set to /home/jenkins/.tmp so every build file should be created within /home/jenkins.
/home/jenkins is set as VOLUME, so it can be reused for a subsequent build, or browsed after the build
as long as the container isn't removed.
Build commands are run inside arbitrary containers, ran as user jenkins (uid:10000, gid:10000) so there's no permission issue accessing the
workspace and other files inside /home/jenkins. This user is automatically created in container user do configure for the build.