Call the target libdir target libdir

Because it's the target libdir.

`--print` uses the same terminology, and it's a simple way to make it
obviously different from `$sysroot/lib`.

src/bootstrap/src/core/build_steps/check.rs

@@ -91,8 +91,8 @@ fn run(self, builder: &Builder<'_>) {
         // We skip populating the sysroot in non-zero stage because that'll lead
         // to rlib/rmeta conflicts if std gets built during this session.
         if compiler.stage == 0 {
-            let libdir = builder.sysroot_libdir(compiler, target);
+            let libdir = builder.sysroot_target_libdir(compiler, target);
-            let hostdir = builder.sysroot_libdir(compiler, compiler.host);
+            let hostdir = builder.sysroot_target_libdir(compiler, compiler.host);
             add_to_sysroot(builder, &libdir, &hostdir, &libstd_stamp(builder, compiler, target));
         }
         drop(_guard);
@@ -257,8 +257,8 @@ fn run(self, builder: &Builder<'_>) {
             false,
         );
 
-        let libdir = builder.sysroot_libdir(compiler, target);
+        let libdir = builder.sysroot_target_libdir(compiler, target);
-        let hostdir = builder.sysroot_libdir(compiler, compiler.host);
+        let hostdir = builder.sysroot_target_libdir(compiler, compiler.host);
         add_to_sysroot(builder, &libdir, &hostdir, &librustc_stamp(builder, compiler, target));
     }
 }

src/bootstrap/src/core/build_steps/compile.rs

@@ -220,7 +220,7 @@ fn run(self, builder: &Builder<'_>) {
                 .join("bin");
             if src_sysroot_bin.exists() {
                 let target_sysroot_bin =
-                    builder.sysroot_libdir(compiler, target).parent().unwrap().join("bin");
+                    builder.sysroot_target_libdir(compiler, target).parent().unwrap().join("bin");
                 t!(fs::create_dir_all(&target_sysroot_bin));
                 builder.cp_link_r(&src_sysroot_bin, &target_sysroot_bin);
             }
@@ -334,7 +334,7 @@ fn copy_third_party_objects(
             && (target.contains("linux") || target.contains("fuchsia"))
     {
         let libunwind_path =
-            copy_llvm_libunwind(builder, target, &builder.sysroot_libdir(*compiler, target));
+            copy_llvm_libunwind(builder, target, &builder.sysroot_target_libdir(*compiler, target));
         target_deps.push((libunwind_path, DependencyType::Target));
     }
 
@@ -347,7 +347,8 @@ fn copy_self_contained_objects(
     compiler: &Compiler,
     target: TargetSelection,
 ) -> Vec<(PathBuf, DependencyType)> {
-    let libdir_self_contained = builder.sysroot_libdir(*compiler, target).join("self-contained");
+    let libdir_self_contained =
+        builder.sysroot_target_libdir(*compiler, target).join("self-contained");
     t!(fs::create_dir_all(&libdir_self_contained));
     let mut target_deps = vec![];
 
@@ -655,8 +656,8 @@ fn run(self, builder: &Builder<'_>) {
             let hostdir = sysroot.join(lib).join("rustlib").join(compiler.host).join("lib");
             (libdir, hostdir)
         } else {
-            let libdir = builder.sysroot_libdir(target_compiler, target);
+            let libdir = builder.sysroot_target_libdir(target_compiler, target);
-            let hostdir = builder.sysroot_libdir(target_compiler, compiler.host);
+            let hostdir = builder.sysroot_target_libdir(target_compiler, compiler.host);
             (libdir, hostdir)
         };
 
@@ -723,7 +724,7 @@ fn copy_sanitizers(
     }
 
     let mut target_deps = Vec::new();
-    let libdir = builder.sysroot_libdir(*compiler, target);
+    let libdir = builder.sysroot_target_libdir(*compiler, target);
 
     for runtime in &runtimes {
         let dst = libdir.join(&runtime.name);
@@ -801,7 +802,7 @@ fn run(self, builder: &Builder<'_>) -> Vec<(PathBuf, DependencyType)> {
 
         let src_dir = &builder.src.join("library").join("rtstartup");
         let dst_dir = &builder.native_dir(target).join("rtstartup");
-        let sysroot_dir = &builder.sysroot_libdir(for_compiler, target);
+        let sysroot_dir = &builder.sysroot_target_libdir(for_compiler, target);
         t!(fs::create_dir_all(dst_dir));
 
         for file in &["rsbegin", "rsend"] {
@@ -1287,10 +1288,17 @@ fn rustc_llvm_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetSelect
     }
 }
 
+/// `RustcLink` copies all of the rlibs from the rustc build into the previous stage's sysroot.
+/// This is necessary for tools using `rustc_private`, where the previous compiler will build
+/// a tool against the next compiler.
+/// To build a tool against a compiler, the rlibs of that compiler that it links against
+/// must be in the sysroot of the compiler that's doing the compiling.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 struct RustcLink {
+    /// The compiler whose rlibs we are copying around.
     pub compiler: Compiler,
-    pub target_compiler: Compiler,
+    /// This is the compiler into whose sysroot we want to copy the rlibs into.
+    pub previous_stage_compiler: Compiler,
     pub target: TargetSelection,
     /// Not actually used; only present to make sure the cache invalidation is correct.
     crates: Vec<String>,
@@ -1300,7 +1308,7 @@ impl RustcLink {
     fn from_rustc(rustc: Rustc, host_compiler: Compiler) -> Self {
         Self {
             compiler: host_compiler,
-            target_compiler: rustc.compiler,
+            previous_stage_compiler: rustc.compiler,
             target: rustc.target,
             crates: rustc.crates,
         }
@@ -1317,12 +1325,12 @@ fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
     /// Same as `std_link`, only for librustc
     fn run(self, builder: &Builder<'_>) {
         let compiler = self.compiler;
-        let target_compiler = self.target_compiler;
+        let previous_stage_compiler = self.previous_stage_compiler;
         let target = self.target;
         add_to_sysroot(
             builder,
-            &builder.sysroot_libdir(target_compiler, target),
+            &builder.sysroot_target_libdir(previous_stage_compiler, target),
-            &builder.sysroot_libdir(target_compiler, compiler.host),
+            &builder.sysroot_target_libdir(previous_stage_compiler, compiler.host),
             &librustc_stamp(builder, compiler, target),
         );
     }
@@ -1770,7 +1778,7 @@ fn run(self, builder: &Builder<'_>) -> Compiler {
 
         // We prepend this bin directory to the user PATH when linking Rust binaries. To
         // avoid shadowing the system LLD we rename the LLD we provide to `rust-lld`.
-        let libdir = builder.sysroot_libdir(target_compiler, target_compiler.host);
+        let libdir = builder.sysroot_target_libdir(target_compiler, target_compiler.host);
         let libdir_bin = libdir.parent().unwrap().join("bin");
         t!(fs::create_dir_all(&libdir_bin));
 
@@ -1854,8 +1862,9 @@ fn run(self, builder: &Builder<'_>) -> Compiler {
         if let Some(enzyme_install) = enzyme_install {
             let lib_ext = std::env::consts::DLL_EXTENSION;
             let src_lib = enzyme_install.join("build/Enzyme/libEnzyme-19").with_extension(lib_ext);
-            let libdir = builder.sysroot_libdir(build_compiler, build_compiler.host);
+            let libdir = builder.sysroot_target_libdir(build_compiler, build_compiler.host);
-            let target_libdir = builder.sysroot_libdir(target_compiler, target_compiler.host);
+            let target_libdir =
+                builder.sysroot_target_libdir(target_compiler, target_compiler.host);
             let dst_lib = libdir.join("libEnzyme-19").with_extension(lib_ext);
             let target_dst_lib = target_libdir.join("libEnzyme-19").with_extension(lib_ext);
             builder.copy_link(&src_lib, &dst_lib);
@@ -1923,7 +1932,7 @@ fn run(self, builder: &Builder<'_>) -> Compiler {
         let sysroot = builder.sysroot(target_compiler);
         let rustc_libdir = builder.rustc_libdir(target_compiler);
         t!(fs::create_dir_all(&rustc_libdir));
-        let src_libdir = builder.sysroot_libdir(build_compiler, host);
+        let src_libdir = builder.sysroot_target_libdir(build_compiler, host);
         for f in builder.read_dir(&src_libdir) {
             let filename = f.file_name().into_string().unwrap();
 

src/bootstrap/src/core/build_steps/dist.rs

@@ -459,7 +459,8 @@ fn prepare_image(builder: &Builder<'_>, compiler: Compiler, image: &Path) {
 
             // Copy over lld if it's there
             if builder.config.lld_enabled {
-                let src_dir = builder.sysroot_libdir(compiler, host).parent().unwrap().join("bin");
+                let src_dir =
+                    builder.sysroot_target_libdir(compiler, host).parent().unwrap().join("bin");
                 let rust_lld = exe("rust-lld", compiler.host);
                 builder.copy_link(&src_dir.join(&rust_lld), &dst_dir.join(&rust_lld));
                 let self_contained_lld_src_dir = src_dir.join("gcc-ld");
@@ -474,7 +475,8 @@ fn prepare_image(builder: &Builder<'_>, compiler: Compiler, image: &Path) {
                 }
             }
             if builder.tool_enabled("wasm-component-ld") {
-                let src_dir = builder.sysroot_libdir(compiler, host).parent().unwrap().join("bin");
+                let src_dir =
+                    builder.sysroot_target_libdir(compiler, host).parent().unwrap().join("bin");
                 let ld = exe("wasm-component-ld", compiler.host);
                 builder.copy_link(&src_dir.join(&ld), &dst_dir.join(&ld));
             }

src/bootstrap/src/core/build_steps/test.rs

@@ -800,7 +800,7 @@ fn run(self, builder: &Builder<'_>) {
             .arg(builder.src.join("src/librustdoc/html/static/css/rustdoc.css").to_str().unwrap())
             .env("RUSTC_STAGE", self.compiler.stage.to_string())
             .env("RUSTC_SYSROOT", builder.sysroot(self.compiler))
-            .env("RUSTDOC_LIBDIR", builder.sysroot_libdir(self.compiler, self.compiler.host))
+            .env("RUSTDOC_LIBDIR", builder.sysroot_target_libdir(self.compiler, self.compiler.host))
             .env("CFG_RELEASE_CHANNEL", &builder.config.channel)
             .env("RUSTDOC_REAL", builder.rustdoc(self.compiler))
             .env("RUSTC_BOOTSTRAP", "1");
@@ -1722,7 +1722,7 @@ fn run(self, builder: &Builder<'_>) {
         // of them!
 
         cmd.arg("--compile-lib-path").arg(builder.rustc_libdir(compiler));
-        cmd.arg("--run-lib-path").arg(builder.sysroot_libdir(compiler, target));
+        cmd.arg("--run-lib-path").arg(builder.sysroot_target_libdir(compiler, target));
         cmd.arg("--rustc-path").arg(builder.rustc(compiler));
 
         // Minicore auxiliary lib for `no_core` tests that need `core` stubs in cross-compilation
@@ -2583,7 +2583,7 @@ fn prepare_cargo_test(
     // by `Cargo::new` and that actually makes things go wrong.
     if builder.kind != Kind::Miri {
         let mut dylib_path = dylib_path();
-        dylib_path.insert(0, PathBuf::from(&*builder.sysroot_libdir(compiler, target)));
+        dylib_path.insert(0, PathBuf::from(&*builder.sysroot_target_libdir(compiler, target)));
         cargo.env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
     }
 
@@ -2818,7 +2818,7 @@ fn run(self, builder: &Builder<'_>) {
         let libdir = if builder.download_rustc() {
             builder.rustc_libdir(compiler)
         } else {
-            builder.sysroot_libdir(compiler, target).to_path_buf()
+            builder.sysroot_target_libdir(compiler, target).to_path_buf()
         };
         let mut dylib_path = dylib_path();
         dylib_path.insert(0, PathBuf::from(&*libdir));
@@ -2943,7 +2943,7 @@ fn run(self, builder: &Builder<'_>) {
         cmd.run(builder);
 
         // Push all our dylibs to the emulator
-        for f in t!(builder.sysroot_libdir(compiler, target).read_dir()) {
+        for f in t!(builder.sysroot_target_libdir(compiler, target).read_dir()) {
             let f = t!(f);
             let name = f.file_name().into_string().unwrap();
             if helpers::is_dylib(&name) {

src/bootstrap/src/core/build_steps/tool.rs

@@ -466,7 +466,7 @@ pub fn command(builder: &Builder<'_>) -> BootstrapCommand {
         let compiler = builder.compiler_for(builder.top_stage, host, host);
         let mut cmd = command(builder.ensure(ErrorIndex { compiler }));
         let mut dylib_paths = builder.rustc_lib_paths(compiler);
-        dylib_paths.push(PathBuf::from(&builder.sysroot_libdir(compiler, compiler.host)));
+        dylib_paths.push(PathBuf::from(&builder.sysroot_target_libdir(compiler, compiler.host)));
         add_dylib_path(dylib_paths, &mut cmd);
         cmd
     }

src/bootstrap/src/core/builder/mod.rs

@@ -1163,7 +1163,7 @@ pub fn sysroot(&self, compiler: Compiler) -> PathBuf {
 
     /// Returns the libdir where the standard library and other artifacts are
     /// found for a compiler's sysroot.
-    pub fn sysroot_libdir(&self, compiler: Compiler, target: TargetSelection) -> PathBuf {
+    pub fn sysroot_target_libdir(&self, compiler: Compiler, target: TargetSelection) -> PathBuf {
         #[derive(Debug, Clone, Hash, PartialEq, Eq)]
         struct Libdir {
             compiler: Compiler,
@@ -1211,7 +1211,7 @@ fn run(self, builder: &Builder<'_>) -> PathBuf {
     }
 
     pub fn sysroot_codegen_backends(&self, compiler: Compiler) -> PathBuf {
-        self.sysroot_libdir(compiler, compiler.host).with_file_name("codegen-backends")
+        self.sysroot_target_libdir(compiler, compiler.host).with_file_name("codegen-backends")
     }
 
     /// Returns the compiler's libdir where it stores the dynamic libraries that