webrick/httpservelet/cgi_runner: avoid IO#reopen on pathname

IO#reopen seems to behave strangely on Win32 based on the logs
posted by Greg for [Bug #14420].  Lets try to fix the issue by
using File.open explicitly (but not Kernel#open).

* lib/webrick/httpservelet/cgi_runner: use File.open explicitly
  [Bug #14220]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61409 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/webrick/httpservlet/cgi_runner.rb

@@ -23,11 +23,11 @@ STDIN.binmode
 
 len = sysread(STDIN, 8).to_i
 out = sysread(STDIN, len)
-STDOUT.reopen(out, "w")
+STDOUT.reopen(File.open(out, "w"))
 
 len = sysread(STDIN, 8).to_i
 err = sysread(STDIN, len)
-STDERR.reopen(err, "w")
+STDERR.reopen(File.open(err, "w"))
 
 len  = sysread(STDIN, 8).to_i
 dump = sysread(STDIN, len)