MFC r311565:

Link llvm-ar to llvm-ranlib, if WITH_CLANG_EXTRAS is enabled. When
invoked as llvm-ranlib, it can create an archive symbol table for
archives of objects compiled for LTO by an LLVM compiler.

Submitted by: Dan McGregor <danismostlikely@gmail.com>

MFC r311806:

After r311565, also remove llvm-ranlib from ObsoleteFiles.inc.