[Bug c/77650] struct with a nested flexible array followed by another member accepted

[kees at outflux dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77650

--- Comment #13 from Kees Cook <kees at outflux dot net> ---
We've been systematically cleaning up Linux in preparation for enabling
-Wflex-array-member-not-at-end, but it's a long road.

I had to go digging into the Linux kernel to figure out why Clang was _not_
warning: it builds with -Wno-gnu since we also build with -std=gnu11.

So... while Linux would prefer to avoid this being added to -Wall right now, it
also isn't new territory: we have to disable stuff getting added to -Wall all
the time. ;)