pyarchive Jenkins support

A set of example Jenkinsfiles for building and testing the Python libstore/libjournal/libarchive prototypes in various ways.

no-parameters-posix-sh

• The pipeline takes no parameters and all branches are fixed at main.
• The main scripts called by Jenkins are written in POSIX sh.

no-parameters-bash

• The pipeline takes no parameters and all branches are fixed at main.
• The main scripts called by Jenkins are written in bash, not POSIX sh.