[scudo][standalone] Remove the pthread key from the shared TSD

[cryptoad]

Summary

https://reviews.llvm.org/D87420 removed the uses of the pthread key,
but the key itself was left in the shared TSD registry. It is created
on registry initialization, and destroyed on registry teardown.

There is really no use for it now, so we can just remove it.

[pcc]

LGTM

[cferris]

Good with Android and LGTM.

compiler-rt/lib/scudo/standalone/tsd_shared.h

 #endif
 
 namespace scudo {
 
 template <class Allocator, u32 TSDsArraySize, u32 DefaultTSDCount>
 struct TSDRegistrySharedT {
   void initLinkerInitialized(Allocator *Instance) {
     Instance->initLinkerInitialized();
-    CHECK_EQ(pthread_key_create(&PThreadKey, nullptr), 0); // For non-TLS
     for (u32 I = 0; I < TSDsArraySize; I++)
       TSDs[I].initLinkerInitialized(Instance);
     const u32 NumberOfCPUs = getNumberOfCPUs();
     setNumberOfTSDs((NumberOfCPUs == 0) ? DefaultTSDCount
                                         : Min(NumberOfCPUs, DefaultTSDCount));
     Initialized = true;
   }
   void init(Allocator *Instance) {
     memset(this, 0, sizeof(*this));
     initLinkerInitialized(Instance);
   }
 
-  void unmapTestOnly() {
-    setCurrentTSD(nullptr);
-    pthread_key_delete(PThreadKey);
-  }
+  void unmapTestOnly() { setCurrentTSD(nullptr); }
 
   ALWAYS_INLINE void initThreadMaybe(Allocator *Instance,
                                      UNUSED bool MinimalInit) {
     if (LIKELY(getCurrentTSD()))
       return;
     initThread(Instance);
   }
 
if (N > 1U) {
         return CandidateTSD;
       }
     }
     // Last resort, stick with the current one.
     CurrentTSD->lock();
     return CurrentTSD;
   }
 
-  pthread_key_t PThreadKey;
   atomic_u32 CurrentIndex;
   u32 NumberOfTSDs;
   u32 NumberOfCoPrimes;
   u32 CoPrimes[TSDsArraySize];
   bool Initialized;
   HybridMutex Mutex;
   HybridMutex MutexTSDs;
   TSD<Allocator> TSDs[TSDsArraySize];
 };
 
 } // namespace scudo
 
 #endif // SCUDO_TSD_SHARED_H_