MFC r348677 (by emaste):

move llvm-ar and llvm-nm to appropriate location in OptionalObsoleteFiles.inc

After r348610 make delete-old was still removing llvm-ar and llvm-nm
(and associated man pages).

Reported by: jhb
Sponsored by: The FreeBSD Foundation

MFC r348761 (by jkim):

Move llvm-ranlib to appropriate location in OptionalObsoleteFiles.inc.

Note llvm-ar is linked to llvm-ranlib since r311565. r348677 fixed
"make delete-old" issue with llvm-ar but missed it somehow.

Discussed with: emaste, jhb