IIRC this means you have either libev but the libevent headers installed
or the other way around, not sure anymore. Please check which of the
libev* packages you have installed.

root@debian:~/dect/libdect# dpkg --get-selections | grep libev
libev-dev                     
                  install
libev3                                          install
libevent-1.4-2                                  install
libevent-core-1.4-2                             install
libevent-dev                                    install
libevent-extra-1.4-2                            install
root@debian:~/dect/libdect#


Fixed by install libev-libevent-dev package