don't need tmpdir for hello world mtest

Author: hone

mrblib/setup.rb

@@ -74,19 +74,14 @@ def test_main
     def bintest
       <<BINTEST
 require 'open3'
-require 'tmpdir'
 
 BIN_PATH = File.join(File.dirname(__FILE__), "../mruby/bin/#{@name}")
 
 assert('setup') do
-  Dir.mktmpdir do |tmp_dir|
-    Dir.chdir(tmp_dir) do
-      output, status = Open3.capture2("\#{BIN_PATH}")
+  output, status = Open3.capture2("\#{BIN_PATH}")
 
-      assert_true status.success?, "Process did not exit cleanly"
-      assert_include output, "Hello World"
-    end
-  end
+  assert_true status.success?, "Process did not exit cleanly"
+  assert_include output, "Hello World"
 end
 BINTEST
     end