[vm/dbc] Add UNREACHABLE() stubs to simulator_dbc.cc in 32-bit mode to make 32-build work

Issue https://github.com/dart-lang/sdk/issues/36665

Change-Id: I3690bac0ad213ea1757a78a14e513ccd8967f92b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/99741
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
Auto-Submit: Martin Kustermann <kustermann@google.com>
diff --git a/runtime/vm/simulator_dbc.cc b/runtime/vm/simulator_dbc.cc
index 873e821..6f2defd 100644
--- a/runtime/vm/simulator_dbc.cc
+++ b/runtime/vm/simulator_dbc.cc
@@ -2646,6 +2646,24 @@
     UNREACHABLE();
     DISPATCH();
   }
+
+  {
+    BYTECODE(UnboxInt64, A_D);
+    UNREACHABLE();
+    DISPATCH();
+  }
+
+  {
+    BYTECODE(BoxInt64, A_D);
+    UNREACHABLE();
+    DISPATCH();
+  }
+
+  {
+    BYTECODE(WriteIntoMint, A_D);
+    UNREACHABLE();
+    DISPATCH();
+  }
 #endif  // defined(ARCH_IS_64_BIT)
 
   // Return and return like instructions (Instrinsic).