Build step to run scripts in a separate shell process. Needs
bash to run.
(bash ctx cwd & optional-env-and-commands)
step that executes commands in a bash. arguments are the working-directory and at least one command to execute returns stdout and stderr as :out value, the exit code as :exit and succeeds if exit-code was 0
deprecated in 0.13.1
(kill was-killed-indicator proc ctx kill-cookie)