bug#41709: installed-os test failing

[Mathieu Othacehe]

> Now multiple options:
>
> * Revert this commit.
> * Find other system closure improvements.
> * Up the limit to 1.5GiB.
>
> WDYT?

Digging a bit more, I discovered multiple culprits in the image closure
size.

* "openssh" is dragging "xauth" which drags some X libraries (but this
does not account for much).

* "sudo" is dragging "python" for about 100MiB.

* "info-reader" is dragging "perl" (and is in fact the same size as
"texinfo" because of a mistake that I introduced with
614a1e3fa2d731d4719f03912b1b87fb4fd309cb) for about 100MiB.

* The switch to non-canonical version of "glibc" and "coreutils" to fix
system cross-compilation in dfc8ccbf5da96a67eb1cade499f0def21e7fdb02 is
also responsible for about 100MiB.

All in all, fixing all of this makes the closure size to drop below 1GiB
which is already a good first step.

I'll try to provide patches soon.

Thanks,

Mathieu