GH-49738: [R][CI] Re-enable GCC+LTO job once rhub has a GCC 15 image

[thisisnic]

Rationale for this change

We removed a job as it was too old and didn't reflect CRAN and now we added it in as we have one which does reflect CRAN's environments

What changes are included in this PR?

Add GCC 15 job

Are these changes tested?

On CI, sure

Are there any user-facing changes?

Nah

• GitHub Issue: [R][CI] Re-enable GCC+LTO job once rhub has a GCC 15 image #49738

[github-actions]

⚠️ GitHub issue #49738 has been automatically assigned in GitHub to PR creator.

[jonkeane]

The error

══ Failed tests ════════════════════════════════════════════════════════════════
── Error ('test-dplyr-filter.R:295:5'): Filtering on a column that doesn't exist errors correctly ──
<validation_error/rlang_error/error/condition>
Error in `not_a_col == 42`: object 'not_a_col' not found
Backtrace:
...

is coming from:

arrow/r/tests/testthat/test-dplyr-filter.R

Lines 295 to 302 in 36c8c9a

	expect_warning(
	expect_error(
	tbl |> record_batch() |> filter(not_a_col == 42) |> collect(),
	"objet 'not_a_col' introuvable"
	),
	NA
	)
	})

Which makes it seem like there's something up with translations / locale not being quite right in the runner / our setup

[thisisnic]

There were changes in #37811 that never got merged as it got complex, which I'll add in here so hopefully those should help