I have recently been investigating how to compile VirtualBox versions 4.3.12 and 5.2.34 on Windows, only to realize that the documentation is very incomplete and that many issues will prevent you from doing it successfully. It took me a long time, but i eventually got it working. Given the unnecessary and tedious complexities, i thought it was a good idea to document my findings and share them with the rest of you, so it is humanly possible to compile these two versions. I have published the necessary tools, libraries and instructions on my website so you can grab them conveniently from there.
http://neonfloppy.sytes.net/resources/compiling/