distcheck fails on CentOS 7

../../../../src/lib/asiolink/io_asio_socket.h:31:39: fatal error: ext/coroutine/coroutine.hpp: No such file or directory
 #include <ext/coroutine/coroutine.hpp>

more details in: https://jenkins.aws.isc.org/view/Kea-manual/job/kea-manual/job/distcheck/4/execution/node/108/log/

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