[libc-commits] [libc] [libc] Add `vsscanf` function (PR #97529)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 approved this pull request.

Looks fine as is, but I'd change the invocations like
```c
auto fn = [](const char *str, const char *fmt, ...) -> int { ... };
fn("Not an Integer", %d, &result);
```

https://github.com/llvm/llvm-project/pull/97529