Credits for this idea go to @myhro who suggested emulating uname.
I cleaned his changes up somewhat and moved the script into a
separate file to make things easier to look at.
I did a test build of wheezy with my changes and the modules were
installed correctly.
root@localhost:/home/vagrant# dkms status
vboxguest, 4.3.20, 3.2.0-4-amd64, x86_64: installed
root@localhost:/home/vagrant# lsmod | egrep ^vbox
vboxsf 33359 0
vboxvideo 12437 0
vboxguest 162115 1 vboxsf
