Add initial ClearLinux support for testing RPM build

[pccowboy]

What does this PR do?

This adds RPM packaging support sufficient for testing installation of the datadog agent on Clearlinux

Motivation

Experimenting with using clearlinux

Additional Notes

The existing dependency scanning creates a dependency on /bin/sh in the resulting RPM. I cannot find a way to inject %define __requires_exclude ^/bin/sh$ using omnibus, unless I manually create the spec.erb described at https://github.com/chef/omnibus/blob/3e43293a0eff95c4175c983247b737a2ce137e35/docs/Building%20on%20RHEL.md

Any suggestions on how to do this are welcomed. Clearlinux installs /bin/sh as part of a different package entirely as part of the os-core bundle installation.

Describe your test plan

rpm -ivh --force datadog-agent-7.26.0-1.x86_64.rpm; datadog-agent configcheck

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[bkabrda]

Hi 👋 thanks for opening the PR.

I think the problem here is that the autogenerated /bin/sh dependency is generated for a reason - for example, the omnibus/package-scripts/agent/postinst script that your PR modifies has #!/bin/sh as the interpreter and AFAICT running on a system that doesn't have /bin/sh, it would just fail. There are more scripts that use /bin/sh as their interpreter as well. I'm not very familiar with Clear Linux, but I'll try to take a look at this and see what the best solution might be.

[bkabrda]

Ok, after getting more familiar with Clear Linux, I see where the problem is now:

Since Clear Linux is not primarily an RPM-based distribution, rpm can be installed on it, but the RPM database is empty (initially), so there is no package that provides /bin/sh in RPM terms, even if /bin/sh is actually present on the filesystem (installed via the os-core bundle).

I think that perhaps removing the /bin/sh dependency might be the right way to go, but I will have to investigate a little bit more what effect that would have on installation on all the RPM-based platforms that we support today. I'll update this discussion when I have a better understanding of whether or not we can do this change.

[bkabrda]

First of all, sorry for not responding further on this for a long time.

As for the solution, is it an option for you to use containerized agent as described in Datadog docs? That's generally a good way to go, unless there's something the containerized agent can't do on ClearLinux (in which case we'd love to hear specific issues).

[pccowboy]

Hello -
We are not currently planning to allow containerized applications to run on our production infrastructure.

We have tried to build a virtual RPM so that the RPM db reflects that /bin/sh is installed. Is that a valid enough workaround that you could accept this PR?

cc:onfleet-ablair