Add flags to force or prevent setting of isolate.is_memory_constrained.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 5b41f926d9e75763829ddf3d77463f205358d184..32f292080f8c64ffcb5196e63567e7289c65d45a 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -624,7 +624,8 @@ bool SetResourceConstraints(ResourceConstraints* constraints) {
     uintptr_t limit = reinterpret_cast<uintptr_t>(constraints->stack_limit());
     isolate->stack_guard()->SetStackLimit(limit);
   }
-  if (constraints->is_memory_constrained().has_value) {
+  if (constraints->is_memory_constrained().has_value &&
+      !i::FLAG_force_memory_constrained.has_value) {
     isolate->set_is_memory_constrained(
         constraints->is_memory_constrained().value);
   }