When the specfile has CR-LF as the line separator, rpm gets confused and does not execute commands properly. For example, if the command is: make rpm attempts to execute: make\r Converting the spec file to UNIX format alleviates the problem. However, this is not always easily done, since a user may desire to merely rebuild a SRC.RPM package.
At the current time, rpm runs only on machines where newline is used as a line separator.