[compiler-rt] [compiler-rt] Do not assume pthread_key_t to be a scalar type. (PR #70786)

[A. Jiang via llvm-commits]

================
@@ -143,7 +143,7 @@ class SPSSerializationTraits<SPSUnwindSectionInfo, UnwindSectionInfo> {
 namespace {
 struct TLVDescriptor {
   void *(*Thunk)(TLVDescriptor *) = nullptr;
-  unsigned long Key = 0;
+  pthread_key_t Key = { 0 };
----------------
frederick-vs-ja wrote:

```suggestion
  pthread_key_t Key = {};
```

https://github.com/llvm/llvm-project/pull/70786