Try to fix Opensuse certificate errors.

[fruffy-bfn]

The OpenSuse repository keeps failing to download the p4lang debian packages. Maybe updating the deprecated key installation technique can help?

@rst0git I can not quite figure out how to fix this. Do maybe know how to fix the key installation issue?

I believe the OpenSuse repository is malformed? It does not have a dists folder. I managed to work around that, but I still run into key issues.

[rst0git]

There are updated installation instructions at
https://software.opensuse.org//download.html?project=home%3Ap4lang&package=p4lang-p4c

echo "deb http://download.opensuse.org/repositories/home:/p4lang/xUbuntu_${DISTRIB_RELEASE}/ /" | sudo tee /etc/apt/sources.list.d/home:p4lang.list
curl -fsSL https://download.opensuse.org/repositories/home:p4lang/xUbuntu_${DISTRIB_RELEASE}/Release.key | gpg --dearmor | sudo tee /etc/apt/trusted.gpg.d/home_p4lang.gpg > /dev/null
sudo apt-get update

[fruffy-bfn]

This does seem to work! Thanks for pointing to the right instructions, could not figure out how install the key. Apparently this approach is still deemed insecure because it installs the key globally, but this should not matter for CI...

[rst0git]

It might be good to also update the README.md file.