Bug#1021402: reproducible: Please force merged-/usr for build2

[Simon McVittie]

On Fri, 07 Oct 2022 at 18:07:45 +0100, Luca Boccassi wrote:
> Wouldn't it be sufficient to create the build2 chroot as merged-usr
> from the start?

That would also be fine, but I think the way the reproducible-builds
infrastructure works is that it caches a single (non-merged-/usr)
pbuilder tarball per suite and converts it to merged-/usr on-demand
for build2, to avoid having to cache essentially the same content twice.
The important thing here is that one of the two builds should be
merged-/usr, and the other should not.

Having a merged-/usr pbuilder tarball and unmerging it with
dpkg-fsys-usrunmess for one of the two builds would also work, but I
suspect that would be less reliable than starting from non-merged-/usr and
merging one of the builds but not the other.

    smcv