Supports the UNIX setuid-on-exec sudo helper. Documents the model,
generates an extra ROMFS user and /etc/sudoers for a non-root test,
reports BINFS modes from the builtin table so ls -l matches execute
bits, and skips NULL environment entries when sanitizing a setuid exec.
Signed-off-by: Abhishek Mishra <mishra.abhishek2808@gmail.com>
