[CI] Run some jobs in Julia v1.12

[giordano]

No description provided.

[giordano]

  Unable to automatically download/install artifact 'GCCBootstrap-x86_64-linux-gnu.v6.1.0.x86_64-linux-musl.unpacked' from sources listed in '/home/runner/work/BinaryBuilderBase.jl/BinaryBuilderBase.jl/Artifacts.toml'.
  Sources attempted:
  - https://pkg.julialang.org/artifact/f06816590c9d1cbffb35d8d2fd342f9c4a462e1c
      Error: SystemError: flush: No space left on device
  - https://github.com/JuliaPackaging/Yggdrasil/releases/download/GCCBootstrap-v6.1.0+3/GCCBootstrap-x86_64-linux-gnu.v6.1.0.x86_64-linux-musl.unpacked.tar.gz
      Error: SystemError: flush: No space left on device

This explains (1) the error and (2) why this started suddenly, without any special change on our side: we simply got over the available storage for whatever reason, maybe even because of changes in the GitHub Actions images, who knows.

[giordano]

All good now after cleaning up more space at the beginning. For the record, we seem to use ~28 GB during the Docker tests, before the tests:

 --> df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        73G   25G   49G  34% /
 --> df -a /
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/root       76026616 25389028  50621204  34% /

after the tests:

 --> df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        73G   53G   21G  73% /
 --> df -a /
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/root       76026616 54757520  21252712  73% /