Add a new command that makes running CI scripts easy. The user goes to
the git repository of choice, which has CI scripts written in a certain
format, and then runs 'pmbootstrap ci' to get an interactive selection
of which of the available scripts to run (or "all"). Specifying one or
multiple scripts on the command-line is also possible, e.g.
$ pmbootstrap ci flake8
$ pmbootstrap ci shellcheck flake8 pytest
$ pmbootstrap ci --all
pmbootstrap then either runs the selected scripts in a chroot (and
installs dependencies as defined at the beginning of the CI scripts), or
natively (with checks inside the scripts for having dependencies
installed). Running natively is needed for .ci/pytest.sh in this
pmbootstrap.git repository, as pmbootstrap can't run inside pmbootstrap.
Running natively or in chroot is defined in an "# Options: " comment
inside the script file.
Documentation for this command and how script files look like:
https://postmarketos.org/pmb-ci
0bcd58765c