GNUmakefile.in: append resources always

* cygwin/GNUmakefile.in (EXTOBJS): override to add resource files
  always.  [ruby-core:67153] [Bug #10657]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49042 b2dd03c8-39d4-4d8f-98ff-823fe69b080e