When compiling daemontools (or any other djb programs) you may end up getting some kind of error regarding errno.h or ERRNO.

While there are patches out there for each program (djbdns, qmail, daemontools, etc), there is an even simpler way.

Look for a file called conf-cc in the source distribution, edit it with your favorite text editor and add -include /usr/include/errno.h to the end of the line.

You should end up with something like this:

gcc -O2 -include /usr/include/errno.h