feat: Port exportLibs.py script to python-gardenlinux-lib

[Leon-hk]

What this PR does / why we need it:

• Includes the exportLibs.py script from feat: add container-python-dev for multi-stage builds gardenlinux#3695 in python-gardenlinux-lib

Usage: (updated)

usage: gl-build [-h] [--output-dir OUTPUT_DIR] [--package-dir PACKAGE_DIR]
                {export-python-libs}

Special notes for your reviewer:

Feel free to criticise a lot, this is my first contribution to python-gardenlinux-lib. I also do not know which version to put into the docstrings

[NotTheEvilOne]

I think the proper package name would be gardenlinux.build. We could add a __main__.py there that currently accepts one command line argument export-python-libs.

The command line script could be named gl-build.

[NotTheEvilOne]

Looks good so far now. Could you please add some unit tests to check for the command line tool to actually produce the result you are expecting?

[Leon-hk]

I've added a test for the exporter. A test for the entire setup is also contained in #3914. I think testing the main program explicitly is not necessary.

[NotTheEvilOne]

Small change, otherwise looks good for me :)

[Leon-hk]

Thank you :) Have you seen Florians message regarding this on Slack?

[NotTheEvilOne]

Thank you :) Have you seen Florians message regarding this on Slack?

Unfortunately I've no access to Slack at the moment.

[Leon-hk]

I've created a Teams group, hope you can access it