collectargs behaviour on argc==0

[Sergey Zakharchenko <doublef.mobile@...>]

Hello,

lua.c collectargs seems to assume that argv has at least one element
(the binary's name, by convention). As people have recently
(re)discovered, some OSes (e.g. Linux) don't guarantee that [0] which
enables up some attack vectors [1]. I don't think many people run
standalone Lua setuid, but you might want to check for this anyway for
correctness.

Best regards,

-- 
DoubleF

[0] https://bugzilla.kernel.org/show_bug.cgi?id=8408
[1] https://www.openwall.com/lists/oss-security/2022/01/25/11