Rollup merge of #76667 - matklad:patch-llvm, r=Mark-Simulacrum
Rollup merge of #76667 - matklad:patch-llvm, r=Mark-Simulacrum

Fix CI LLVM to work on NixOS out of the box

r? @Mark-Simulacrum

Tested locally, seems to work!

graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust