[GC] Properly mark Unsubtyping as closed-world (#8029)

This was marked in pass.cpp properly, but not elsewhere.

Author: kripken

scripts/fuzz_opt.py

@@ -2486,7 +2486,8 @@ def write_commands(commands, filename):
                          ("--cfp-reftest",),
                          ("--gsi",),
                          ("--type-ssa",),
-                         ("--type-merging",)}
+                         ("--type-merging",),
+                         ("--unsubtyping",)}
 
 
 def get_random_opts():

src/passes/Unsubtyping.cpp

@@ -446,6 +446,10 @@ struct Unsubtyping : Pass {
       return;
     }
 
+    if (!getPassOptions().closedWorld) {
+      Fatal() << "Unsubtyping requires --closed-world";
+    }
+
     // Initialize the subtype relation based on what is immediately required to
     // keep the code and public types valid.
     analyzePublicTypes(*wasm);

test/lit/passes/issue-7087.wast

@@ -9,7 +9,7 @@
 ;; module-level code in TypeSSA and fix the validator so it would have caught
 ;; the stale type.
 
-;; RUN: wasm-opt %s -all --type-ssa --unsubtyping -S -o - | filecheck %s
+;; RUN: wasm-opt %s -all --type-ssa --unsubtyping --closed-world -S -o - | filecheck %s
 
 (module
  ;; CHECK:      (rec