[ci] [R-package] clang-18 jobs failing

[jameslamb]

Description

Created from #6357 (comment).

r-debian-clang-devel CI jobs are failing for clang 18, with these installation errors:

The following packages have unmet dependencies:
 clangd-18 : Depends: libabsl20220623t64 (>= 0~20220623.0-1) but it is not installable
             Depends: libgrpc++1.51t64 (>= 1.51.1) but it is not installable
             Depends: libgrpc29t64 (>= 1.51.1) but it is not installable
             Depends: libprotobuf32t64 (>= 3.21.12) but it is not installable
 liblldb-18 : Depends: libcurl4t64 (>= 7.16.2) but it is not installable
              Depends: libpython3.11t64 (>= 3.11.5) but it is not installable
 libomp-18-dev : Depends: libpython3.11t64 (>= 3.11.5) but it is not installable
 llvm-18 : Depends: libcurl4t64 (>= 7.16.2) but it is not installable
E: Unable to correct problems, you have held broken packages.

Reproducible example

Any recent CI job, for example https://github.com/microsoft/LightGBM/actions/runs/8231989739/job/22510837736?pr=6357.

Additional Comments

PR where those checks were added: #6265

[jameslamb]

#6357 removed the clang-18 job.

Let's leave this open until that job is restored.

[jameslamb]

This looks relevant: https://unix.stackexchange.com/a/772827/550004

The t64 suffix means the software in question is modified to use 64-bit time_t, so it will be ready for January 19, 2038, when the 32-bit version of time_t will overflow (the Y2K38 problem).

Seems some Debian packages are being renamed to make that distinction clear. All of the packages that error message mentions have the t64 suffix.

[jameslamb]

Maybe the root cause here is those Y2K38 changes happening in Debian AND the fact that the rhub/debian-clang-devel image hasn't been updated in 3 months.

https://hub.docker.com/r/rhub/debian-clang-devel

This relates to #6116. I think that project is abandoned, based on the lack of activity there, things being broken for months, and this conversation: r-hub/rhub-linux-builders#67.