Cleanup tmp output

lib/execjs/external_runtime.rb

@@ -143,19 +143,21 @@ module ExecJS
 
       if ExecJS.windows?
         def exec_runtime(filename)
+          path = Dir::Tmpname.create(['execjs', 'json']) {}
+          begin
             command = binary.split(" ") << filename
-
-          Dir::Tmpname.create(['execjs', 'json']) do |output|
-            `#{shell_escape(*command)} 2>&1 > #{output}`
-            output = File.open(output, 'rb', @popen_options) { |f| f.read }
+            `#{shell_escape(*command)} 2>&1 > #{path}`
+            output = File.open(path, 'rb', @popen_options) { |f| f.read }
+          ensure
+            File.unlink(path) if path
+          end
 
           if $?.success?
-              return output
+            output
           else
             raise RuntimeError, output
           end
         end
-        end
 
         def shell_escape(*args)
           # see http://technet.microsoft.com/en-us/library/cc723564.aspx#XSLTsection123121120120
@@ -164,16 +166,6 @@ module ExecJS
             arg
           }.join(" ")
         end
-
-        # See Tempfile.create on Ruby 2.1
-        def create_tempfile(basename)
-          tmpfile = nil
-          Dir::Tmpname.create(basename) do |tmpname|
-            mode    = File::WRONLY | File::CREAT | File::EXCL
-            tmpfile = File.open(tmpname, mode, 0600)
-          end
-          tmpfile
-        end
       else
         def exec_runtime(filename)
           io = IO.popen(binary.split(' ') << filename, @popen_options.merge({err: [:child, :out]}))