Wait... this is *user mode* code at this point?
Linux kernel headers aren't includable from user space without
processing them through "make headers_install".
However, from looking at the filenames in your list, it doesn't look
like userspace code at all (although they're wrappered to the degree
that it's somewhat hard to tell.) Thus, you're building a kernel
module, not userland.
It sounds like something is seriously broken in your setup, or in the
VirtualBox makefiles. From the looks of it, I would say the latter.
It would help to see how gcc is invoked, but your email message doesn't
include any gcc invocations, and your "full error log" weblink is
broken, so it's hard to say.
-hpa
-