Наткнулся на блестящую фразу тут: http://www.virtualbox.org/wiki/Windows%20build%20instructions

Now, both these roadblocks are solvable — (1) is just a lot of work and (2) is definitely possible (the VirtualBox team has even created binary wrappers between these compilers before) — but we have not yet looked too deeply into it.

All the code is there, feel free to try make it build and work.

Т.е. хрен вам, а не простое решение. Хотите собрать бинарник, который собрала до вас куча других людей — убейте пару недель собственного времени, ибо ритуал. Поубывав бы.