Comment 5 for bug 520364

Not sure why you'd need to do this, we've released 1.1.0 which has this fix in it already. If for whatever reason you can't get binaries for your distro and need to compile from source, then you should at least get the source for 1.1.0 (https://launchpad.net/linuxdcpp/+download). If you still want to add X11 manually, then take a look at the commit that fixed it:

http://bazaar.launchpad.net/~linuxdcpp-team/linuxdcpp/trunk/revision/350