[compiler-rt] [libcxxabi] [libunwind] [runtimes][PAC] Harden unwinding when possible (#138571) (PR #143230)

[Oliver Hunt via llvm-commits]

ojhunt wrote:

Ok a bunch of these errors are because clang is misdiagnosing this scenario

```cpp
namespace {
template <class T> void foo(T*){}
}

template <class T> void bar(T* t) {
    foo(t);
}
```
as not using the template function `foo`

https://github.com/llvm/llvm-project/pull/143230