[asan] nuke yet another async-signal-safety bug in UAR (oh, my)

llvm-svn: 191080

compiler-rt/lib/asan/asan_fake_stack.h

@@ -77,6 +77,7 @@ class FakeStack {
   }
 
   void Destroy() {
+    PoisonAll(0);
     UnmapOrDie(this, RequiredSize(stack_size_log_));
   }
 

compiler-rt/lib/asan/asan_thread.h

@@ -77,7 +77,6 @@ class AsanThread {
 
   void DeleteFakeStack() {
     if (!fake_stack_) return;
-    fake_stack_->PoisonAll(0);
     FakeStack *t = fake_stack_;
     fake_stack_ = 0;
     SetTLSFakeStack(0);