Steps to reproduce on a fresh install of Ubuntu Bionic:
export DEBIAN_FRONTEND=noninteractive && apt update && apt install curl wget htop git vim ccache -y && git clone https://github.com/bitcoin/bitcoin.git ./bitcoin-core && cd bitcoin-core && apt install build-essential libtool autotools-dev automake pkg-config bsdmainutils python3-zmq libevent-dev libboost-system-dev libboost-filesystem-dev libboost-test-dev libboost-thread-dev libsqlite3-dev libdb++-dev gcc-8 g++-8 -y && ./autogen.sh && CXX=g++-8 CC=gcc-8 ./configure --without-incompatible-bdb && make -j $(nproc)
Output:
CXXLD bitcoind
libbitcoin_util.a(libbitcoin_util_a-system.o): In function `boost::system::error_category::std_category::equivalent(std::error_code const&, int) const':
/usr/include/boost/system/error_code.hpp:686: undefined reference to `boost::system::generic_category()'
/usr/include/boost/system/error_code.hpp:689: undefined reference to `boost::system::generic_category()'
/usr/include/boost/system/error_code.hpp:701: undefined reference to `boost::system::generic_category()'
libbitcoin_util.a(libbitcoin_util_a-system.o): In function `boost::system::error_category::std_category::equivalent(int, std::error_condition const&) const':
/usr/include/boost/system/error_code.hpp:656: undefined reference to `boost::system::generic_category()'
/usr/include/boost/system/error_code.hpp:659: undefined reference to `boost::system::generic_category()'
libbitcoin_util.a(libbitcoin_util_a-system.o):/usr/include/boost/system/error_code.hpp:206: more undefined references to `boost::system::generic_category()' follow
libbitcoin_util.a(libbitcoin_util_a-system.o): In function `__static_initialization_and_destruction_0':
/usr/include/boost/system/error_code.hpp:210: undefined reference to `boost::system::system_category()'
libbitcoin_util.a(libbitcoin_util_a-system.o): In function `_GLOBAL__sub_I_BITCOIN_CONF_FILENAME':
/usr/include/boost/asio/error.hpp:230: undefined reference to `boost::system::system_category()'
collect2: error: ld returned 1 exit status
Makefile:5708: recipe for target 'bitcoind' failed
make[2]: *** [bitcoind] Error 1
make[2]: Leaving directory '/bitcoin-core/src'
Makefile:16758: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/bitcoin-core/src'
Makefile:814: recipe for target 'all-recursive' failed
make: *** [all-recursive] Error 1
Initial report by @hebasto in #20744 (comment)