During the build process, attestation-agent uses `.git` folder to check the git commit hash:

https://github.com/confidential-containers/guest-components/blob/main/attestation-agent/attestation-agent/build.rs#L68

Since OSBS is removing .git folder the attestation-agent build will fail with:

```
2024-06-18 23:55:53,020 - atomic_reactor.tasks.binary_container_build - INFO - — stderr
2024-06-18 23:55:53,020 - atomic_reactor.tasks.binary_container_build - INFO - thread 'main' panicked at attestation-agent/attestation-agent/build.rs:71:14:
2024-06-18 23:55:53,024 - atomic_reactor.tasks.binary_container_build - INFO - called `Result::unwrap()` on an `Err` value: Os

```

We need to fix that. A few solutions I could think at the moment:

1. Adapt upstream code to query environment variables in case .git does not exist. (And use CI_<REPO_NAME>_UPSTREAM_COMMIT in Dockerfile template)
2. Investigate if OSBS could preserve .git folder
3. Create a fake git repo (ugly?)