[$] Handling argc==0 in the kernel

By now, most readers are likely to be familiar with the Polkit vulnerability known as CVE-2021-4034.The fix for Polkit is relatively straightforward and is being rolled outacross the net. The root of this problem, though, lies in amisunderstanding about how programs are run on Unix-like systems. Thisproblem is highly likely to exist in other programs, so it would be nice tofind a more general solution. The best place to address this issue may bein the kernel, but properly working around thismisunderstanding without causing regressions is not an easy task.