src/librustc_codegen_llvm/build.rs

fn main() {
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-env-changed=CFG_VERSION");
    println!("cargo:rerun-if-env-changed=CFG_PREFIX");
    println!("cargo:rerun-if-env-changed=CFG_LLVM_ROOT");
}