Ray, I too have the same error message as Marc when compiling a fresh copy of firmware onto a fully updated / dist-update Jessie formatted SD card. I tried compiling another SD card and again I got the same error message.
The result of this is that OpenSprinkler doesn’t run, checked /etc/init.d/OpenSprinkler.sh to find that that file has no content. I copied the content of OpenSprinkler.sh from my other Ospi running firmware 2.1.8(4) into the new build with no success.