Ensure LLVM is in the link path for rustc tools

src/bootstrap/builder.rs

@@ -11,7 +11,7 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::time::{Duration, Instant};
 
-use build_helper::t;
+use build_helper::{output, t};
 
 use crate::cache::{Cache, Interned, INTERNER};
 use crate::check;
@@ -23,7 +23,7 @@ use crate::install;
 use crate::native;
 use crate::test;
 use crate::tool;
-use crate::util::{self, add_dylib_path, exe, libdir};
+use crate::util::{self, add_dylib_path, add_link_lib_path, exe, libdir};
 use crate::{Build, DocTests, GitRepo, Mode};
 
 pub use crate::Compiler;
@@ -1034,6 +1034,20 @@ impl<'a> Builder<'a> {
                 .env("RUSTC_SNAPSHOT_LIBDIR", self.rustc_libdir(compiler));
         }
 
+        // Tools that use compiler libraries may inherit the `-lLLVM` link
+        // requirement, but the `-L` library path is not propagated across
+        // separate Cargo projects. We can add LLVM's library path to the
+        // platform-specific environment variable as a workaround.
+        //
+        // Note that this is disabled if LLVM itself is disabled or we're in a
+        // check build, where if we're in a check build there's no need to build
+        // all of LLVM and such.
+        if self.config.llvm_enabled() && self.kind != Kind::Check && mode == Mode::ToolRustc {
+            let llvm_config = self.ensure(native::Llvm { target });
+            let llvm_libdir = output(Command::new(&llvm_config).arg("--libdir"));
+            add_link_lib_path(vec![llvm_libdir.trim().into()], &mut cargo);
+        }
+
         if self.config.incremental {
             cargo.env("CARGO_INCREMENTAL", "1");
         } else {

src/bootstrap/util.rs

@@ -72,6 +72,31 @@ pub fn dylib_path() -> Vec<PathBuf> {
     env::split_paths(&var).collect()
 }
 
+/// Adds a list of lookup paths to `cmd`'s link library lookup path.
+pub fn add_link_lib_path(path: Vec<PathBuf>, cmd: &mut Command) {
+    let mut list = link_lib_path();
+    for path in path {
+        list.insert(0, path);
+    }
+    cmd.env(link_lib_path_var(), t!(env::join_paths(list)));
+}
+
+/// Returns the environment variable which the link library lookup path
+/// resides in for this platform.
+fn link_lib_path_var() -> &'static str {
+    if cfg!(target_env = "msvc") { "LIB" } else { "LIBRARY_PATH" }
+}
+
+/// Parses the `link_lib_path_var()` environment variable, returning a list of
+/// paths that are members of this lookup path.
+fn link_lib_path() -> Vec<PathBuf> {
+    let var = match env::var_os(link_lib_path_var()) {
+        Some(v) => v,
+        None => return vec![],
+    };
+    env::split_paths(&var).collect()
+}
+
 /// `push` all components to `buf`. On windows, append `.exe` to the last component.
 pub fn push_exe_path(mut buf: PathBuf, components: &[&str]) -> PathBuf {
     let (&file, components) = components.split_last().expect("at least one component required");