Fix some errors from UBSan.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 3af1f3694b089533b614c41d7eaa7a86be8b49a1..4ed0793fa99666770af0f9bd18773f57af2726bb 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -4554,7 +4554,7 @@ static uint32_t FinalizeHash(uint32_t hash, intptr_t hashbits) {
   hash += hash << 3;
   hash ^= hash >> 11;  // Logical shift, unsigned hash.
   hash += hash << 15;
-  hash &= ((static_cast<intptr_t>(1) << hashbits) - 1);
+  hash &= ((static_cast<uintptr_t>(1) << hashbits) - 1);
   return (hash == 0) ? 1 : hash;
 }