`Option<&T>` has the same ABI layout as `*const T`, so we have some room for
improvement where we get more Rust convenience. Further, a bug is fixed where
INVALID_PARAMETER wasn't returned when the BUFFER_SIZE pointer is NULL.
See UEFI 2.10 13.2.2. EFI_LOAD_FILE2_PROTOCOL.LoadFile() for reference.
When booting without Secure Boot active, it is not necessary to defend
against a malicious command line being passed from the loader. So just
use it in this case, to facilitaty some debugging and recovery use
cases.
Fixes: https://github.com/nix-community/lanzaboote/issues/226
nikstur