This file is indexed.

/usr/lib/clang/6.0.0/include is in libclang-common-6.0-dev 1:6.0-1ubuntu2.

This file is owned by root:root, with mode 0o777.

It is a symlink to /usr/lib/clang/6.0.0/../../llvm-6.0/lib/clang/6.0.0/include