Fix oras ArtifactHub config push

hack/release/common.sh

@@ -58,7 +58,7 @@ build() {
   commit_sha="${4}"
 
   date_epoch="$(dateEpoch)"
-  build_date="$(buildDate "${date_epoch}")"
+  build_date="$(buildDate)"
 
   img="$(GOFLAGS=${GOFLAGS:-} SOURCE_DATE_EPOCH="${date_epoch}" KO_DATA_DATE_EPOCH="${date_epoch}" KO_DOCKER_REPO="${oci_repo}" ko publish -B -t "${version}" ./cmd/controller)"
   img_repo="$(echo "${img}" | cut -d "@" -f 1 | cut -d ":" -f 1)"
@@ -91,7 +91,11 @@ publishHelmChart() {
   yq e -i ".version = \"${version}\"" "charts/${helm_chart}/Chart.yaml"
 
   cd charts
-  [[ -s "${ah_config_file_name}" ]] && oras push "${oci_repo}/${helm_chart}:artifacthub.io" --config /dev/null:application/vnd.cncf.artifacthub.config.v1+yaml "${ah_config_file_name}:application/vnd.cncf.artifacthub.repository-metadata.layer.v1.yaml"
+  if [[ -s "${ah_config_file_name}" ]]; then
+    temp=$(mktemp)
+    echo {} > "${temp}"
+    oras push "${oci_repo}/${helm_chart}:artifacthub.io" --config "${temp}:application/vnd.cncf.artifacthub.config.v1+yaml" "${ah_config_file_name}:application/vnd.cncf.artifacthub.repository-metadata.layer.v1.yaml"
+  fi
   helm dependency update "${helm_chart}"
   helm lint "${helm_chart}"
   helm package "${helm_chart}" --version "${version}"
@@ -119,11 +123,7 @@ dateEpoch() {
 }
 
 buildDate() {
-  local date_epoch
-
-  date_epoch="${1}"
-
-  date -u --date="@${date_epoch}" "+%Y-%m-%dT%H:%M:%SZ" 2>/dev/null
+  date -u -r "$(git log -1 --format='%ct')" "+%Y-%m-%dT%H:%M:%SZ"
 }
 
 prepareWebsite() {