Fix duplicate file warnings.
    
    The find-debuginfo.sh script will return duplicate entries of
    certain files even though the input is uinque. This results
    in rpm build warnings like this:
    ~~~
    Processing files: glibc-debuginfo-common-2.17.90-10.fc20.x86_64
    warning: File listed twice: /usr/lib/debug/usr/sbin/build-locale-archive.debug
    warning: File listed twice: /usr/lib/debug/usr/sbin/nscd.debug
    warning: File listed twice: /usr/lib/debug/usr/sbin/zdump.debug
    warning: File listed twice: /usr/lib/debug/usr/sbin/zic.debug
    ~~~
    
    The solutions is to make the output file list uinque by post
    processing it after it is output by find-debuginfo.sh.
    
    The solution removes the warnings and produces no visible
    change in the output rpms.