Function needs_directory_placeholder 

pub fn needs_directory_placeholder(backend: &BackendCapabilities) -> bool

Whether a run on the backend whose capabilities are backend needs the placeholder directory hermit-cli mounts for Detcore (Config::directory_placeholder): where the guest’s procfs is not the kernel’s, as one capability says (procfs_inode::tool_can_name_guest_descriptors). Where it is the kernel’s, Detcore’s served /proc directories are open on that procfs’s root, and hermit-cli mounts nothing for them.