There is an updated pull request by CameronNemo against master on the void-packages repository

https://github.com/CameronNemo/void-packages R-cran-archive
https://github.com/void-linux/void-packages/pull/38438

xbps-src: fetch from CRAN archive
CRAN has a lovely practice of moving the latest releases into an archive
after a new release is made. So when pillar 1.8.0 is released, for
example, version 1.7.0 gets moved into the archive.

Add the CRAN archive as a mirror to handle this case.

See below for an example:

```
=> R-cran-pillar-1.5.1_1: running do-fetch hook: 00-distfiles ...
=> R-cran-pillar-1.5.1_1: fetching distfile 'pillar_1.5.1.tar.gz' from 'https://cran.r-project.org/src/contrib/Archive/pillar'...
```

#### Testing the changes
- I tested the changes in this PR: **briefly**

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A patch file from https://github.com/void-linux/void-packages/pull/38438.patch is attached