CI: Add more Debian packages to the llvm-passes rootfs image

[DilumAluthge]

• We need bash for the test suite.
• We need less for the doctests.
• Also, sort the entries of packages in alphabetical order to make it easier to find specific entries in the list.

[DilumAluthge]

After this PR is merged, how do I generate the new rootfs image and upload it to https://github.com/JuliaCI/rootfs-images?

E.g. do I just need to run julia llvm-passes.jl on a Debian machine, and it will do the upload and everything?

[DilumAluthge]

For posterity, here's a setup that worked for me:

On your local machine, run these commands:

$ git clone git@github.com:JuliaLang/julia.git
$ docker run --privileged --rm -it -v $(pwd):/root/workspace julia:buster /bin/bash

Now, inside the Docker container, run these commands:

# cd
# apt-get update && apt-get -y install debootstrap sudo
# cd /root/workspace/julia/.buildkite/rootfs_images/
# rm -rf ~/.julia
# julia -e 'using Pkg; Pkg.add(["Scratch", "ghr_jll"]); Pkg.update()'
# julia -e 'using Pkg; Pkg.precompile()'
# export GITHUB_TOKEN="my-github-token-goes-here"
# julia llvm-passes.jl

[staticfloat]

Why do we need gfortran for LLVM passes?

[DilumAluthge]

Good question. It was already in the list previously, so I didn't remove it.

[staticfloat]

Oh, right, of course, we build Julia here. I had this confused with analyzegc.

[DilumAluthge]

Should I keep overwriting the v1 tag, or should I make new tags v1.1, v1.2, etc?

[staticfloat]

We should not overwrite anything used by older CI runs, if we can help it.