added trigger annotation (elastic#40990) (elastic#41004)

(cherry picked from commit 40743f8)

Co-authored-by: Olga Naydyonock <olga.naidjonoka@elastic.co>

Author: mergify[bot]

.buildkite/hooks/pre-command

@@ -6,6 +6,13 @@ set -euo pipefail
 # https://buildkite.com/docs/pipelines/managing-log-output#redacted-environment-variables
 PRIVATE_CI_GCS_CREDENTIALS_PATH="kv/ci-shared/platform-ingest/gcp-platform-ingest-ci-service-account"
 
+if [[ "${BUILDKITE_LABEL:-}" == *"Pipeline upload"* || "${BUILDKITE_LABEL:-}" == *"Upload Pipeline"* ]]; then
+
+  if [[ "${GITHUB_PR_TRIGGER_COMMENT:-}" != "" ]]; then
+    buildkite-agent annotate "**No changes.** Triggered from comment: _${GITHUB_PR_TRIGGER_COMMENT}_" --style "info" --context 'ctx-info'
+  fi
+fi
+
 if [[ "$BUILDKITE_PIPELINE_SLUG" == "beats-xpack-packetbeat" && "$BUILDKITE_STEP_KEY" == *"system-tests"* ]]; then
     PRIVATE_CI_GCS_CREDENTIALS_SECRET=$(retry -t 5 -- vault kv get -field plaintext -format=json ${PRIVATE_CI_GCS_CREDENTIALS_PATH})
     export PRIVATE_CI_GCS_CREDENTIALS_SECRET