pack is not using invokebuiltin anymore

test/ruby/test_jit.rb

@@ -21,6 +21,9 @@ class TestJIT < Test::Unit::TestCase
     :defineclass,
     :opt_call_c_function,
 
+    # to be tested
+    :invokebuiltin,
+
     # never used
     :opt_invokebuiltin_delegate,
   ].each do |insn|
@@ -596,12 +599,6 @@ class TestJIT < Test::Unit::TestCase
     skip "support this in opt_call_c_function (low priority)"
   end
 
-  def test_compile_insn_invokebuiltin
-    insns = collect_insns(RubyVM::InstructionSequence.of([0].method(:pack)).to_a)
-    mark_tested_insn(:invokebuiltin, used_insns: insns)
-    assert_eval_with_jit('print [0].pack("c")', stdout: "\x00", success_count: 1)
-  end
-
   def test_compile_insn_opt_invokebuiltin_delegate_leave
     insns = collect_insns(RubyVM::InstructionSequence.of("\x00".method(:unpack)).to_a)
     mark_tested_insn(:opt_invokebuiltin_delegate_leave, used_insns: insns)