[clang] [NFC][analyzer] Extract general logic in security.ArrayBound (PR #210774)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

> This is a semantic change.

Nice euphemism for "bug" :sweat_smile: Old behavior restored in https://github.com/llvm/llvm-project/pull/210774/commits/fd86bcdef6119cc5f1736b903e061c9c46b4d4a3. I really should have added a test for this zero-size element case earlier.

I also added a FIXME to avoid reporting this case (accessing the 6th element in an array of 10 zero-sized elements), I intend to fix this in a non-NFC follow-up PR. @steakhal Do you agree that this is a false positive and shouldn't be reported -- or do you know about some quirk of the standard that justifies reporting it?

I also added https://github.com/llvm/llvm-project/pull/210774/commits/947d88db187f90dec04176fa391e3bc3ff3c9e37 which should _finally_ fix the CI which was still broken after my earlier patch.

https://github.com/llvm/llvm-project/pull/210774