Michelangelo Riccobene

Example error reported by clang-coverage: ``` In file included from /home/builder/project/node/silkworm/downloader/messages/OutboundGetBlockHeaders.cpp:22: /home/builder/project/node/silkworm/downloader/header_downloader.hpp:73:7: error: unknown attribute 'long_running' ignored [-Werror,-Wunknown-attributes] [[long_running]] void receive_messages(MessageQueue& messages, // subscribe with sentry to receive messages ^...

The decision to ignore unrecognized attributes is not mine, it was taken by the c++ standardization committee. Anyway I close this issue to not waste time, but we will lose...

Downloader command is only for test/dev purpose. Anyway I will fix it.

This now is fixed.