Revert "ART: Disable check under memory tools"

This reverts commit 820c13bea5795e04986bf617319517562de76514.

The check is valid, the whole stack setup is broken.
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 748dfa5..f1f4a12 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -940,10 +940,7 @@
   }
 
   // Sanity check.
-  if (RUNNING_ON_MEMORY_TOOL == 0) {
-    // Sanitizers may be using a split stack. Ignore the check.
-    CHECK_GT(FindStackTop(), reinterpret_cast<void*>(tlsPtr_.stack_end));
-  }
+  CHECK_GT(FindStackTop(), reinterpret_cast<void*>(tlsPtr_.stack_end));
 
   return true;
 }