One suggestion:
If we introduce virtualbox as a build dependency (as it is due to vboxmanage), we should take care that it is properly installed/configured. I.e. we should also pull the respective kernel-headers. Even if we just need vboxmanage for the VM build process, pulling virtualbox without ensuring that it’s setup correctly due to missing kernel-headers doesn’t sound too good to me (might be confusing to users). That said, pulling kernel-headers wouldn’t interfere with a possible Oracle virtualbox neither, needed anyways - whether Debian or Oracle (I’m sorry that I haven’t commented yet within the respective thread - I’m a bit busy the next week(s)).
I though keeping it as simple as possible for builders and keeping the reasoning as a reference in the footnotes would be best. Some of these explanations need to be quite long so they don’t sound stupid. If it was 1 short sentence, it would still require “see footnote for more”. What do you think?
Should we add GRUB and dkpg error from this post?
Yes.
That would be a known bug,a terrible one because it slows down the build a lot and should be fixed. Please refresh my mind, did I succeed fixing this in Whonix 8?
It should more or less cover your suggestion. With the only limitation, that it fails open. As the info message explains, I guess this is the best approach here. Please check.