head.hackage seems broken since Jan 10th

sheaf
2026-01-14T22:00:36Z

It seems that head.hackage has been failing since Jan 10th, judging by the Grafana dashboard.

Errors are of the form:

```
> /nix/store/140hd9zyzzvf8d8cscmgp85md3l9sqr9-binutils-2.43.1/bin/ld: cannot find -lgmp: No such file or directory
> collect2: error: ld returned 1 exit status
> : error:
> `gcc' failed in phase `Linker'. (Exit code: 1)
>
For full logs, run 'nix log /nix/store/iw5dh9f2kfgz17hbciagsk66fiv6p9k0-ghc-9.15.20260114.drv'.
```

See e.g. [here](https://gitlab.haskell.org/ghc/head.hackage/-/jobs/2392840#L624) and [here](https://gitlab.haskell.org/ghc/head.hackage/-/jobs/2392841#L617).

I asked @MangoIV if he had any ideas but a cursory investigation didn't reveal anything. Perhaps @teo might have an idea of what changed that could cause the pipelines to start failing?