Block builder used to iterate mempool chunks in mining order while assembling a block.
Declared in <txmempool.h>
[[guarded_by(0x7fb95f554ff8), guarded_by(0x7fb968bc6708), guarded_by(0x7fb95fdd0548), guarded_by(0x7fb978b75908), guarded_by(0x7fb96b8fae68), guarded_by(0x7fb96e5c1938), guarded_by(0x7fb97a07b968), guarded_by(0x7fb96be436b8)]]
mutable
std::unique_ptr<TxGraph::BlockBuilder> m_builder;