[clang] [analyzer] Fix core.VLASize checker false positive taint reports (PR #68140)

[Daniel Krupp via cfe-commits]

dkrupp wrote:

I executed the analysis with this patch on the following open source projects: memcached,tmux,curl,twin,vim,openssl,sqlite,ffmpeg,postgres, xerces

And it did not bring any visible change in the reports. So there were no new or resolved findings compared to the baseline.
In both the baseline and the new analysis execution the  alpha.security.taint.TaintPropagation and the core.VLASize checkers were enabled.

Link to the diff:
https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?review-status=Unreviewed&review-status=Confirmed%20bug&detection-status=New&detection-status=Reopened&detection-status=Unresolved&run=%2avla_taint_baseline&is-unique=off&newcheck=%2avla_taint_new&diff-type=New&checker-msg=%2ataint%2a

https://github.com/llvm/llvm-project/pull/68140