I just tried to compile daemontools (Broken link ~~http://cr.yp.to/daemontools/~~), ucspi-tcp (Broken link http://cr.yp.to/ucspi-tcp/) etc on RedHat 9 and found that they all error in a similar way, complaining about errno.h

Apparently its caused by RedHat using glibc-2.3.1, some nice fellow has created patches for all the djb tools here (Broken link http://qmail.cbn.net.id/moni.csi.hu/pub/glibc-2.3.1/)

Read more here (Broken link http://qmail.cbn.net.id/moni.csi.hu/pub/glibc-2.3.1/README)