Use Ubuntu 20.04 for building

[egbertbouman]

Fixes #8242.

I removed cpio=2.13+dfsg-7 since it isn't needed nor is version 2.13+dfsg-7 available on Ubuntu 20.04.

[qstokkink]

I verified on my Ubuntu 24.04 that this works.

IIRC cpio, alien and rpm were necessary for the cx_Freeze build process before it used makedist_debian.sh, maybe the other two are also unnecessary now.

[synctext]

Work on Ubuntu 20.04 👍

[egbertbouman]

validate

[egbertbouman]

Turns out the alien and rpm dependencies were needed after all (or al least one of them is..).
The only change is I made is an apt-get update which seemed to be needed.

[qstokkink]

Thanks for checking 👍