[clang] [clang][analyzer] fix false positive of BlockInCriticalSectionChecker (PR #126752)

[Gábor Horváth via cfe-commits]

Xazax-hun wrote:

Oh, for functions that are documented to not block on invalid `fd`s, I think it makes sense to skip the warnings when the `fd` is `-1`. 

https://github.com/llvm/llvm-project/pull/126752