Werk #15703: Linux agent updater - Fix missing libcrypt.so.1

Previously, when running the agent updater, either manually or automatically, it may crash immediately with error message:

Error loading Python lib '/tmp/_MEIc9TJOz/libpython3.7m.so.1.0': dlopen: libcrypt.so.1: cannot open shared object file: No such file or directory

Future versions of the agent updater will include the missing library.

Technical background:
This happens on Linux systems that don't come with a libcrypt.so.1 any longer.
The cmk-update-agent executable is supposed to include all needed libraries.
However, in this case, the build mechanism failed to find the linked library.

If you ran into this problem, you will have to reinstall the Checkmk agent (including the agent updater) on affected hosts after updating your Checkmk site and baking agents.

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