Vagrant: Successive builds without reboot fail to write boot code to image.

[JonahBraun]

When building with Vagrant, the first build produces a working image. A second build however will fail to write boot code to the image. That is, in the second image file, at 0x2000 there is nothing but 0s while the first image file contains code.

Workaround: After restarting Vagrant, the next build will produce a working image.

Steps to reproduce:

git clone https://github.com/armbian/build.git
cd build

# Change virtual box name so it plays nicely with existing installations.
sed 's/Armbian Builder/Armbian Bug Test/' Vagrantfile > newVagrant
mv newVagrant Vagrantfile

# as a separate bug, output directory must exist and currently does not
mkdir -p output

vagrant up

vagrant ssh -c 'cd armbian && sudo ./compile.sh\
  BRANCH=default BOARD=pine64so KERNEL_ONLY=no RELEASE=xenial\
  KERNEL_CONFIGURE=no BUILD_DESKTOP=no PROGRESS_DISPLAY=plain'
mv output/images/*img image_1.works.img

vagrant ssh -c 'cd armbian && sudo ./compile.sh\
  BRANCH=default BOARD=pine64so KERNEL_ONLY=no RELEASE=xenial\
  KERNEL_CONFIGURE=no BUILD_DESKTOP=no PROGRESS_DISPLAY=plain'
mv output/images/*img image_2.fail.img

vagrant halt
vagrant up

vagrant ssh -c 'cd armbian && sudo ./compile.sh\
  BRANCH=default BOARD=pine64so KERNEL_ONLY=no RELEASE=xenial\
  KERNEL_CONFIGURE=no BUILD_DESKTOP=no PROGRESS_DISPLAY=plain'
mv output/images/*img image_3.works.img