Revert "Revert "[analyzer] Ignore IncompleteArrayTypes in getStaticSize() for FAMs""

This reverts commit df1f4e0c.

Now the test case explicitly specifies the target triple.
I decided to use x86_64 for that matter, to have a fixed
bitwidth for `size_t`.

Aside from that, relanding the original changes of:
https://reviews.llvm.org/D105184