Use O_NOFOLLOW_ANY on macOS #179
Description
According to this blog post, macos 11 has a new O_NOFOLLOW_ANY flag that causes open to fail if any path component is a symlink. Assuming symlinks are relatively rare, cap-std could use this as a fast path -- check that the path contains no explicit .. and then open with O_NOFOLLOW_ANY; if that succeeds, then we're done. If either of those fails, open with the slow path.