From an experiment with single-threaded (make -j1) builds it takes 5294 seconds to compile upstream MySQL 8.0.32 from source versus 8443 for FB MySQL 8.0.28. The difference is mostly from the RocksDB build targets (rocksdb_se, ldb, sst_dump) which account for ~2700 seconds (~900 seconds each).
Each of the RocksDB build targets recompiles RocksDB from source. Avoiding that (only compiling RocksDB once) would reduce the build time by ~20%.
From an experiment with single-threaded (make -j1) builds it takes 5294 seconds to compile upstream MySQL 8.0.32 from source versus 8443 for FB MySQL 8.0.28. The difference is mostly from the RocksDB build targets (rocksdb_se, ldb, sst_dump) which account for ~2700 seconds (~900 seconds each).
Each of the RocksDB build targets recompiles RocksDB from source. Avoiding that (only compiling RocksDB once) would reduce the build time by ~20%.