Comment 3 for bug 637240

I agree with you: the builddir is the "natural" place for the list file. However assuming that this file must be specified with the relative path to the builddir has a couple of drawbacks which are not backward compatible:
1) the file cannot be specified with the absolute path name even though it resides into the buildir.
2) people used to place this file somewere else cannot build the packages on systems using different rpm versions.