[clang] [analyzer] Suppress VirtualCall warnings in system headers (PR #184183)

[Gábor Horváth via cfe-commits]

https://github.com/Xazax-hun approved this pull request.

Overall, this looks good to me. In general, we sometimes report errors in system headers because a warning in a system header (e.g., a null dereference) might be the result of the user code doing something bad. But in this particular case, I believe it is very unlikely that the user code is to blame. 

But wait for at least one more perspective on this before merging. 

https://github.com/llvm/llvm-project/pull/184183