Another make target that is necessary to build the package, that is not run by the default target. This must not require root priviledges. Another make target that is necessary to install the package, that is not run by the default target. On Debian systems, these commands may require root or fakeroot. Otherwise, redirect the output to a log file and read the whole thing.
Some packaging systems output a log of messages even after a fatal error.
Then, try and cut out pieces of the pkgwriteinfo file until you locate the problem. Report a bug if the problem is clear. It is easy to forget to rerun configure and very slow. I don't know of any easy solution to forgetting at the moment, but you may just run config.status instead, in order save time. Of course, you can and should work however you want, but for your information, I will write the testing process I use for releasing packages.