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.