[clang] [analyzer] Adjust ExprEngine::VisitDeclStmt to ignore `T v=v;` idiom cases for C code (PR #187530)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat commented:

Overall the change LGTM, I added minor remarks in inline comments.

https://github.com/llvm/llvm-project/pull/187530