[clang] [CIR] Handle global string literals as char array initializer (PR #144384)

[Morris Hafner via cfe-commits]

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

LGTM, just a request for three more test cases. I'm not sure if they work upstream already. If they don't, let's just skip over them for now.

```c++
char oversized[100] = "123";
char exact[4] = "123";

decltype(auto) returns_literal() {
    return "abcd";
}
```

https://github.com/llvm/llvm-project/pull/144384