Merge branch 'jc/make-dedup-ls-files-output'

A "ls-files" that emulates "find" to enumerate files in the working tree resulted in duplicated Makefile rules that caused the build to issue an unnecessary warning during a trial build after merge conflicts are resolved in working tree *.h files but before the resolved results are added to the index. This has been corrected. * jc/make-dedup-ls-files-output: Makefile: dedup list of files obtained from ls-files