9p rootfs issues
Description of problem:
I've created qemu guest per https://wiki.qemu.org/Documentation/9p_root_fs guidelines. debootstrap fails on this guest.
Steps to reproduce:
```
root@ubuntu-dev:~# debootstrap --arch amd64 --variant=minbase noble /var/tmp/new_root/
I: Retrieving InRelease 
I: Checking Release signature
E: Error executing gpgv to check Release signature
root@ubuntu-dev:~# 
```
Additional information:
I noticed, that gpg key extracted by debootstrap from the InRelease is corrupted:
```
root@ubuntu-dev:~# head /var/tmp/new_root/var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_noble_Release.gpg
-----BEGIN PGP SIGNATURE-----
-----BEGIN PGP SIGNATURE-----

-----BEGIN PGP SIGNATURE-----
-----BEGIN PGP SIGNATURE-----

iQIzBAEBCgAdFiEE9uyzdiR07anSG3Aihxkg0ZkbyTwFAmXkbkUACgkQhxkg0Zkb
-----BEGIN PGP SIGNATURE-----
-----BEGIN PGP SIGNATURE-----

root@ubuntu-dev:~# 
```
I also noticed that on the 9p filesystem appending to files corrupts them:
```
root@ubuntu-dev:~# echo 1 >/var/tmp/test
root@ubuntu-dev:~# cat /var/tmp/test
1
root@ubuntu-dev:~# echo 2 >>/var/tmp/test
root@ubuntu-dev:~# cat /var/tmp/test
1
1
2
root@ubuntu-dev:~# 
```
This is not happening on the tmpfs:
```
root@ubuntu-dev:~# echo 1 >/tmp/test
root@ubuntu-dev:~# cat /tmp/test
1
root@ubuntu-dev:~# echo 2 >>/tmp/test
root@ubuntu-dev:~# cat /tmp/test
1
2
root@ubuntu-dev:~# 
```