Fix simple test on platforms where compaction is not supported

844588f made it so that trying to call
gc_verify_compaction_references on unsupported platform result in an
exception rather than a crash. Rescue the exception in a YJIT btest
that uses gc_verify_compaction_references.

bootstraptest/test_yjit.rb

@@ -662,7 +662,11 @@ def foo
   foo
   foo
 
-  GC.verify_compaction_references(double_heap: true, toward: :empty)
+  begin
+    GC.verify_compaction_references(double_heap: true, toward: :empty)
+  rescue NotImplementedError
+    # in case compaction isn't supported
+  end
 
   foo
 }