-Wreturn-stack-address false positive with unreachable code

https://cpp.godbolt.org/z/3357xPfP8

```cpp
#include

template
[[noreturn]] constexpr R __absurd() { std::abort(); }

int const& weird() {
return __absurd();
}
```

Technically, `weird` should return `__absurd()`, but I accidentally wrote it like this and I'm not really sure if this counts as a bug.