Trim MJIT output from TestHideSkip

to prevent failure like
https://app.wercker.com/ruby/ruby/runs/mjit-test1/5cd28aa6ab79a30008ee819b?step=5cd28b2403f44600070db083
with --jit-verbose=1.

test/testunit/test_hideskip.rb

@@ -5,9 +5,13 @@ class TestHideSkip < Test::Unit::TestCase
   def test_hideskip
     assert_not_match(/^ *1\) Skipped/, hideskip)
     assert_match(/^ *1\) Skipped/, hideskip("--show-skip"))
-    assert_match(/assertions\/s.\n+1 tests, 0 assertions, 0 failures, 0 errors, 1 skips/, hideskip("--hide-skip"))
+    output = hideskip("--hide-skip")
+    output.gsub!(/Successful MJIT finish\n/, '') if RubyVM::MJIT.enabled?
+    assert_match(/assertions\/s.\n+1 tests, 0 assertions, 0 failures, 0 errors, 1 skips/, output)
   end
 
+  private
+
   def hideskip(*args)
     IO.popen([*@options[:ruby], "#{File.dirname(__FILE__)}/test4test_hideskip.rb",
                        "--verbose", *args], err: [:child, :out]) {|f|