configure.in: workaround of mingw-w64
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48988 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: workaround of mingw-w64
a bug in mingw-w64 header. [ruby-core:67103] [Bug #10640]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48988 b2dd03c8-39d4-4d8f-98ff-823fe69b080e