dea28d86b4
Require LLVM_CONFIG to be set in rustc_llvm/build.rs
This environment variable should always be set by bootstrap in `rustc_llvm_env`. The fallback is quite ugly and complicated, so removing it is nice.
bf71daedc2/src/bootstrap/src/core/build_steps/compile.rs (L1166)
I tried finding when this was added in git history, but it pointed all the way to "add build scripts" at which point I stopped digging more. This has always been here.
cc `@nikic` `@cuviper` in case you happen to be aware of a deeper reason behind this
r? bootstrap