Fix base AMI hash calculation mismatch

Base AMI lookup failed because main packer hash didn't include variant,
causing hash mismatch between building and looking up base images.

Fixes "No golden base AMI found" errors. Base AMI files can be properly
located in S3.

Author: scadu

.buildkite/steps/packer.sh

@@ -22,7 +22,7 @@ packer_files_sha=$(find Makefile "packer/${os}" plugins/ -type f -print0 | xargs
 internal_files_sha=$(find go.mod go.sum internal/ -type f -print0 | xargs -0 sha256sum | awk '{print $1}' | sort | sha256sum | awk '{print $1}')
 stable_agent_sha=$(curl -Lfs "https://download.buildkite.com/agent/stable/latest/${agent_binary}.sha256")
 unstable_agent_sha=$(curl -Lfs "https://download.buildkite.com/agent/unstable/latest/${agent_binary}.sha256")
-packer_hash=$(echo "$packer_files_sha" "$internal_files_sha" "$arch" "$stable_agent_sha" "$unstable_agent_sha" | sha256sum | awk '{print $1}')
+packer_hash=$(echo "$packer_files_sha" "$internal_files_sha" "$arch" "$stable_agent_sha" "$unstable_agent_sha" "$variant" | sha256sum | awk '{print $1}')
 
 # Include variant in the hash so base and full images don’t clash
 echo "Packer image hash for ${os}/${arch} (${variant}) is ${packer_hash}"