message: Update build script to support GitHub Actions
diff: @@ -4,3 +4,8 @@ if [[ "$KOKORO_BUILD_ID" ]]; then
  echo "Running job $KOKORO_JOB_NAME"
  TARGET=`echo "$KOKORO_JOB_NAME" | awk -F "/" '{print $NF}'`
  fi
  +
  +if [[ "GITHUB_WORKFLOW" ]]; then
  + echo "Running job GITHUB_ACTION in workflow $GITHUB_WORKFLOW"
  + TARGET=`echo "$GITHUB_ACTION" | awk -F "-" '{print $NF}'`
  +fi
  