/usr/lib/llvm-4.0/include/ is in liblld-4.0-dev 1:4.0-1ubuntu1~16.04.2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/llvm-4.0/include/lld/
/usr/lib/llvm-4.0/include/lld/Config/
/usr/lib/llvm-4.0/include/lld/Config/Version.h
/usr/lib/llvm-4.0/include/lld/Core/
/usr/lib/llvm-4.0/include/lld/Core/AbsoluteAtom.h
/usr/lib/llvm-4.0/include/lld/Core/ArchiveLibraryFile.h
/usr/lib/llvm-4.0/include/lld/Core/Atom.h
/usr/lib/llvm-4.0/include/lld/Core/DefinedAtom.h
/usr/lib/llvm-4.0/include/lld/Core/Error.h
/usr/lib/llvm-4.0/include/lld/Core/File.h
/usr/lib/llvm-4.0/include/lld/Core/Instrumentation.h
/usr/lib/llvm-4.0/include/lld/Core/LLVM.h
/usr/lib/llvm-4.0/include/lld/Core/LinkingContext.h
/usr/lib/llvm-4.0/include/lld/Core/Node.h
/usr/lib/llvm-4.0/include/lld/Core/Parallel.h
/usr/lib/llvm-4.0/include/lld/Core/Pass.h
/usr/lib/llvm-4.0/include/lld/Core/PassManager.h
/usr/lib/llvm-4.0/include/lld/Core/Reader.h
/usr/lib/llvm-4.0/include/lld/Core/Reference.h
/usr/lib/llvm-4.0/include/lld/Core/Reproduce.h
/usr/lib/llvm-4.0/include/lld/Core/Resolver.h
/usr/lib/llvm-4.0/include/lld/Core/SharedLibraryAtom.h
/usr/lib/llvm-4.0/include/lld/Core/SharedLibraryFile.h
/usr/lib/llvm-4.0/include/lld/Core/Simple.h
/usr/lib/llvm-4.0/include/lld/Core/SymbolTable.h
/usr/lib/llvm-4.0/include/lld/Core/UndefinedAtom.h
/usr/lib/llvm-4.0/include/lld/Core/Writer.h
/usr/lib/llvm-4.0/include/lld/Driver/
/usr/lib/llvm-4.0/include/lld/Driver/Driver.h
/usr/lib/llvm-4.0/include/lld/ReaderWriter/
/usr/lib/llvm-4.0/include/lld/ReaderWriter/MachOLinkingContext.h
/usr/lib/llvm-4.0/include/lld/ReaderWriter/YamlContext.h
/usr/lib/llvm-4.0/include/lld/Support/
/usr/lib/llvm-4.0/include/lld/Support/Memory.h