[Pkg-rust-maintainers] Bug#1124769: rustc: FTBFS rustc in Debian Bookworm because of conflict in build deps

[Sergei Semin]

Fabian, if you don't like docker for some reasons, I can show way howto
reproduce problem with debootstap.

Just for information, I have RaspberryPI with Ubuntu 22.04.5 LTS and
debootstap 1.0.142 taken from Debian Forky
(https://packages.debian.org/forky/debootstrap)
```
ubuntu at ubuntu:~$ debootstrap --version
debootstrap 1.0.142
ubuntu at ubuntu:~$ apt list --installed | grep debootstrap

WARNING: apt does not have a stable CLI interface. Use with caution in
scripts.

debootstrap/now 1.0.142 all [installed,local]
ubuntu at ubuntu:~$
```

Let's try to reproduce a problem.

Create Debian Bookworm chroot environment in minbase variant:
```
sudo debootstrap --no-check-sig --variant=minbase bookworm bookworm-
chroot-env http://deb.debian.org/debian/ |& tee debootstrap.log
```

debootstrap.log attached to letter just for information.

Only main bookworm repo exists in sources list at this moment:
```
ubuntu at ubuntu:~$ cat bookworm-chroot-env/etc/apt/sources.list
deb http://deb.debian.org/debian bookworm main
ubuntu at ubuntu:~$ ls bookworm-chroot-env/etc/apt/sources.list.d/
ubuntu at ubuntu:~$
```

Add deb-src:
```
echo "deb-src http://deb.debian.org/debian bookworm main" | sudo tee -a
bookworm-chroot-env/etc/apt/sources.list
```

sources.list after this change looks like this:
```
ubuntu at ubuntu:~$ cat bookworm-chroot-env/etc/apt/sources.list
deb http://deb.debian.org/debian bookworm main
deb-src http://deb.debian.org/debian bookworm main
ubuntu at ubuntu:~$
```

Chroot in created environment:
```
sudo chroot bookworm-chroot-env bash
```

Update apt cache:
```
apt update
```

Output in my case:
```
root at ubuntu:/# apt update
Hit:1 http://deb.debian.org/debian bookworm InRelease
Get:2 http://deb.debian.org/debian bookworm/main Sources [9494 kB]
Get:3 http://deb.debian.org/debian bookworm/main Translation-en [6109
kB]
Fetched 15.6 MB in 8s (1918 kB/s)                                     
Reading package lists... Done
Building dependency tree... Done
All packages are up to date.
root at ubuntu:/#
```

And now we can see problem just like in docker earlier in this thread:
```
root at ubuntu:/# apt -s build-dep rustc
Reading package lists... Done
Reading package lists... Done
Building dependency tree... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libstd-rust-web-dev : Conflicts: libstd-rust-dev
 rustc-web : Conflicts: rustc
E: Error, pkgProblemResolver::Resolve generated breaks, this may be
caused by held packages.
root at ubuntu:/#
```

I also checked Debian Bookworm chroot env created in described way in
amd64. I reprpoduced problem in described way.

P.S. We can try to reproduce problem in chroot environment with Trixie
created using debootstrap:
```
sudo debootstrap --no-check-sig --variant=minbase trixie trixie-chroot-
env http://deb.debian.org/debian/ |& tee debootstrap.log
```
But `apt -s build-dep rustc` works ok in Debian Trixie arm64 and amd64.
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