cygwin64でMessageBoxの文字化け回避

#include <windows.h>

// fileencoding=utf-8
// fileformat=utf-8

int WINAPI WinMain(
    HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    LPSTR lpCmdLine,
    int nCmdShow) {

  // 成功
  //LPCWSTR s = L"あいうえお";

  // 成功
  //WCHAR s[] = L"あいうえお";
  //WCHAR const *s = L"あいうえお";
  //const WCHAR *s = L"あいうえお";

  // 成功
  wchar_t s[] = L"あいうえお";
  //wchar_t const *s = L"あいうえお";
  //const wchar_t *s = L"あいうえお";

  MessageBox(NULL, s, s, MB_OK);

  return 0;
}

// x86_64-w64-mingw32-g++ (GCC) 4.8.2
// CYGWIN_NT-6.1 non-pc 1.7.28(0.271/5/3) 2014-02-09 21:06 x86_64 Cygwin

// compile option
// PATH=$PATH:/usr/x86_64-w64-mingw32/sys-root/mingw/bin
// x86_64-w64-mingw32-g++ -DUNICODE -std=c++11 -Wall test.cpp