Add .libPaths() to the test.data.table() diagnostic

[MichaelChirico]

Motivated by r-cmd-check-occasional still failing, which I no longer understand why. See ubuntu-latest log here:

https://github.com/Rdatatable/data.table/actions/runs/9908622817/job/27374799289

We get:

test.data.table('other.Rraw') failed to attach required package(s): ggplot2, hexbin, plyr, dplyr, caret, gdata, nlme, sf, nanotime.

And indeed these packages are missing from "all installed packages". But the previous step (Install dependencies) has those packages installing without error, e.g.

* DONE (ggplot2)

So now I'm wondering if it installed to a different library than is used by the subsequent step (?), otherwise that installed path is removed in between steps (it has _temp in it after all: /home/runner/work/_temp/Library). Anyway this diagnostic seems useful to include.

[github-actions]

Generated via commit bb5c930

Download link for the artifact containing the test results: ↓ atime-results.zip

Time taken to finish the standard R installation steps: 12 minutes and 8 seconds

Time taken to run atime::atime_pkg on the tests: 3 minutes and 24 seconds

[tdhock]

great thanks