[analyzer][CTU][NFC] Add an extra regression test

Before `bc713f6a` landed, the analyzer
crashed on this reduced example.
It seems important to have bot `ctu` and `-analyzer-opt-analyze-headers`
enabled in the example.

This test file ensures that no regression happens in the future in this regard.

Reviewed By: martong, NoQ

Differential Revision: https://reviews.llvm.org/D96586