ci: add script to build/publish zot multiarch images and modify the publish pipeline to use it (#2214)

Example usage:
   scripts/build_multiarch_image.sh --registry ghcr.io/project-zot --source-tag v2.0.0 --file build/multiarch-zot.json --destination-tags="v2.0.0 latest"

Signed-off-by: Andrei Aaron <aaaron@luxoft.com>

scripts/build_multiarch_image.sh

@@ -0,0 +1,124 @@
+#!/bin/bash
+
+input_file=""
+source_tag=""
+destination_tags=""
+registry=""
+debug=0
+
+while (( "$#" )); do
+    case $1 in
+        -r|--registry)
+            if [ -z "$2" ]; then
+                echo "Option registry requires an argument"
+                exit 1
+            fi
+            registry=${2};
+            shift 2
+            ;;
+        --destination-tags)
+            if [ -z "$2" ]; then
+                echo "Option destination-tag requires an argument"
+                exit 1
+            fi
+            destination_tags=${2}
+            shift 2
+            ;;
+        --source-tag)
+            if [ -z "$2" ]; then
+                echo "Option source-tag requires an argument"
+                exit 1
+            fi
+            source_tag=${2}
+            shift 2
+            ;;
+        -f|--file)
+            if [ -z "$2" ]; then
+                echo "Option file requires an argument"
+                exit 1
+            fi
+            input_file=${2}
+            shift 2
+            ;;
+        -d|--debug)
+            debug=1
+            shift 1
+            ;;
+        --)
+            shift 1
+            break
+            ;;
+        *)
+            break
+            ;;
+    esac
+done
+
+if [ -z "${registry}" ]; then
+    echo "Parameter --registry is mandatory"
+    exit 1
+fi
+
+if [ -z "${source_tag}" ]; then
+    echo "Parameter --source-tag is mandatory"
+    exit 1
+fi
+
+if [ -z "${destination_tags}" ]; then
+    destination_tags=${source_tag}
+    echo "Parameter --destination-tags is not provided, will use value of --source-tag: ${destination_tags}"
+fi
+
+if [ -z "${input_file}" ]; then
+    echo "Parameter --file is mandatory"
+    exit 1
+fi
+
+function verify_prerequisites {
+    mkdir -p ${data_dir}
+
+    command -v regctl
+    if [ $? -ne 0 ]; then
+        echo "you need to install regctl as a prerequisite"
+        exit 1
+    fi
+
+    command -v jq
+    if [ $? -ne 0 ]; then
+        echo "you need to install jq as a prerequisite"
+        return 1
+    fi
+
+    return 0
+}
+
+if [ ${debug} -eq 1 ]; then
+    set -x
+    regctl_cmd="${regctl_cmd} -v debug"
+fi
+
+target_repo=$(jq -r -c ".target_repo" ${input_file})
+source_repos=$(jq -r -c '.source_repos[]' ${input_file})
+
+regctl_cmd="regctl"
+
+digest_params=""
+for repo in ${source_repos[@]}; do
+    echo "identifying digest for ${registry}/${repo}:${source_tag}"
+    digest=$(${regctl_cmd} image digest ${registry}/${repo}:${source_tag})
+    echo "identified digest ${digest} for ${registry}/${repo}:${source_tag}"
+
+    ${regctl_cmd} image copy ${registry}/${repo}:${source_tag} ${registry}/${target_repo}@${digest}
+
+    digest_params="--digest ${digest} ${digest_params}"
+done
+
+destination_tags_array=($destination_tags)
+
+echo "creating index ${registry}/${target_repo}:${destination_tags_array[0]}"
+${regctl_cmd} index create ${registry}/${target_repo}:${destination_tags_array[0]} ${digest_params}
+
+for destination_tag in ${destination_tags_array[@]:1}; do
+    echo "tagging ${registry}/${target_repo}:${destination_tags_array[0]} as ${registry}/${target_repo}:${destination_tag}"
+    ${regctl_cmd} image copy ${registry}/${target_repo}:${destination_tags_array[0]} ${registry}/${target_repo}:${destination_tag}
+done