Tests that --fields_may_be_reset, --link_natives_lazily, and --no_allow_absolute_addresses work in …

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 084b8b0f223f458196949b8be849bee66250d40e..f69961260959974f7b33e3b3ff61ae5a6b4ca787 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -264,6 +264,9 @@ class Isolate : public BaseIsolate {
   uword stack_overflow_flags_address() const {
     return reinterpret_cast<uword>(&stack_overflow_flags_);
   }
+  static intptr_t stack_overflow_flags_offset() {
+    return OFFSET_OF(Isolate, stack_overflow_flags_);
+  }
 
   int32_t IncrementAndGetStackOverflowCount() {
     return ++stack_overflow_count_;