/usr/bin/llvm-ar-3.6 is in llvm-3.6 1:3.6.2-3ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../lib/llvm-3.6/bin/llvm-ar
/usr/bin/../lib/llvm-3.6/bin/llvm-ar