There's a merged pull request on the void-packages repository

cross-*: use isl-devel and pkg-config
https://github.com/void-linux/void-packages/pull/42792

Description:
use isl-devel in the toolchain, as well as pkg-config, see #34153

[ci skip]

@leahneukirchen if this makes sense, I'll repeat it for the other cross-* packages