Job is the slave's output of running/completed task.
This is a directory with at least:
* alive
  Constantly "touch"ed file when job is running. That updates file's
  mtime and tells that process is still alive.
* host.txt
  Slave's hostname. It is also used to determine when job was started.
* tmp-path.txt
  Path to temporary directory on the slave, in case it failed and you
  wish to look at its state.
* pkg.txt
  Just list of installed skelpkgs during the build.
* env.txt
  Dump of environment variables used to start each step.
* steps/
  Subdirectory containing more subdirectories named after each step.
  Each of those directories contains at least:
  * started
    Empty file used for creation time determination.
  * stdout.txt, stderr.txt
    => TAI64N-prefixed
    output of corresponding streams.
  * exitcode.txt
    May not exist if step is in progress. Contains either decimal
    value of the step's return code, or "timeout" string in
    case the step is killed due to longtime lack of output.