* ext/etc/etc.c (etc_sysconfdir): mentioned special case on
  Windows.  [ruby-core:43110] [Bug #6121]

* ext/etc/extconf.rb: define SYSCONFDIR only if sysconfdir is set
  in RbConfig::CONFIG and not empty.

* win32/Makefile.sub (config.status): sysconfdir is not used on
  Windows.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60402 b2dd03c8-39d4-4d8f-98ff-823fe69b080e