execveat syscall incorrect with `AT_EMPTY_PATH` flag
We always pass in `/proc/self/exe` which means we end up ignoring this flag.
This causes us to potentially execute a process incorrectly since we are supposed to execute the FD rather whatever is in the arguments.
This is a fairly tricky edge case and not many people (that I'm aware of) are abusing it right now.
Will need a test-case with executing an FD that is a she-bang file, regular ELF, and with and without binfmt_misc.