I came across an issue with the build instructions. Mac OS X, VirtualBox, vagrant. Used the ubuntu16 target in the vagrant file, when I tried to run

make sysprep

it ran into some symlink and file permission errors. I ran it sudo and it worked but then homebrew refused to run. I was able to

chown

all the files that it created before it errorred back to the vagrant user, and manually upgrade brew, and then it built successfully. I couldn’t find anything obvious in the make script but there are some comments about vagrant/vbox hacks so maybe something changes re shared folder permissions.