improvements on initial sysroot and libdir finding logics

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

@@ -1062,7 +1062,7 @@ impl Step for Tidy {
         if builder.config.channel == "dev" || builder.config.channel == "nightly" {
             builder.info("fmt check");
             if builder.initial_rustfmt().is_none() {
-                let inferred_rustfmt_dir = builder.initial_rustc.parent().unwrap();
+                let inferred_rustfmt_dir = builder.initial_sysroot.join("bin");
                 eprintln!(
                     "\
 ERROR: no `rustfmt` binary found in {PATH}

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

@@ -1260,7 +1260,7 @@ impl<'a> Builder<'a> {
     pub fn sysroot_libdir_relative(&self, compiler: Compiler) -> &Path {
         match self.config.libdir_relative() {
             Some(relative_libdir) if compiler.stage >= 1 => relative_libdir,
-            _ if compiler.stage == 0 => &self.build.initial_libdir,
+            _ if compiler.stage == 0 => &self.build.initial_relative_libdir,
             _ => Path::new("lib"),
         }
     }

src/bootstrap/src/core/config/config.rs

@@ -360,6 +360,7 @@ pub struct Config {
     pub initial_cargo: PathBuf,
     pub initial_rustc: PathBuf,
     pub initial_cargo_clippy: Option<PathBuf>,
+    pub initial_sysroot: PathBuf,
 
     #[cfg(not(test))]
     initial_rustfmt: RefCell<RustfmtState>,
@@ -1541,8 +1542,6 @@ impl Config {
             );
         }
 
-        config.initial_cargo_clippy = cargo_clippy;
-
         config.initial_rustc = if let Some(rustc) = rustc {
             if !flags.skip_stage0_validation {
                 config.check_stage0_version(&rustc, "rustc");
@@ -1558,19 +1557,18 @@ impl Config {
                 .join(exe("rustc", config.build))
         };
 
+        config.initial_sysroot = config.initial_rustc.ancestors().nth(2).unwrap().into();
+
+        config.initial_cargo_clippy = cargo_clippy;
+
         config.initial_cargo = if let Some(cargo) = cargo {
             if !flags.skip_stage0_validation {
                 config.check_stage0_version(&cargo, "cargo");
             }
             cargo
         } else {
             config.download_beta_toolchain();
-            config
-                .out
-                .join(config.build)
-                .join("stage0")
-                .join("bin")
-                .join(exe("cargo", config.build))
+            config.initial_sysroot.join("bin").join(exe("cargo", config.build))
         };
 
         // NOTE: it's important this comes *after* we set `initial_rustc` just above.

src/bootstrap/src/core/download.rs

@@ -427,9 +427,8 @@ impl Config {
         let version = &self.stage0_metadata.compiler.version;
         let host = self.build;
 
-        let bin_root = self.out.join(host).join("stage0");
-        let clippy_stamp = bin_root.join(".clippy-stamp");
-        let cargo_clippy = bin_root.join("bin").join(exe("cargo-clippy", host));
+        let clippy_stamp = self.initial_sysroot.join(".clippy-stamp");
+        let cargo_clippy = self.initial_sysroot.join("bin").join(exe("cargo-clippy", host));
         if cargo_clippy.exists() && !program_out_of_date(&clippy_stamp, date) {
             return cargo_clippy;
         }

src/bootstrap/src/lib.rs

@@ -161,7 +161,7 @@ pub struct Build {
     initial_rustc: PathBuf,
     initial_cargo: PathBuf,
     initial_lld: PathBuf,
-    initial_libdir: PathBuf,
+    initial_relative_libdir: PathBuf,
     initial_sysroot: PathBuf,
 
     // Runtime state filled in later on
@@ -315,46 +315,19 @@ impl Build {
         let in_tree_llvm_info = config.in_tree_llvm_info.clone();
         let in_tree_gcc_info = config.in_tree_gcc_info.clone();
 
-        let initial_target_libdir_str = if config.dry_run() {
-            "/dummy/lib/path/to/lib/".to_string()
-        } else {
-            output(
-                Command::new(&config.initial_rustc)
-                    .arg("--target")
-                    .arg(config.build.rustc_target_arg())
-                    .arg("--print")
-                    .arg("target-libdir"),
-            )
-        };
+        let initial_target_libdir_str =
+            config.initial_sysroot.join("lib/rustlib").join(config.build).join("lib");
+
         let initial_target_dir = Path::new(&initial_target_libdir_str).parent().unwrap();
         let initial_lld = initial_target_dir.join("bin").join("rust-lld");
 
-        let initial_sysroot = if config.dry_run() {
-            "/dummy".to_string()
-        } else {
-            output(Command::new(&config.initial_rustc).arg("--print").arg("sysroot"))
-        }
-        .trim()
-        .to_string();
-
-        // FIXME(Zalathar): Determining this path occasionally fails locally for
-        // unknown reasons, so we print some extra context to help track down why.
-        let find_initial_libdir = || {
-            let initial_libdir =
-                initial_target_dir.parent()?.parent()?.strip_prefix(&initial_sysroot).ok()?;
-            Some(initial_libdir.to_path_buf())
-        };
-        let Some(initial_libdir) = find_initial_libdir() else {
-            panic!(
-                "couldn't determine `initial_libdir`:
-- config.initial_rustc:      {rustc:?}
-- initial_target_libdir_str: {initial_target_libdir_str:?}
-- initial_target_dir:        {initial_target_dir:?}
-- initial_sysroot:           {initial_sysroot:?}
-",
-                rustc = config.initial_rustc,
-            );
-        };
+        let initial_relative_libdir = initial_target_dir
+            .ancestors()
+            .nth(2)
+            .unwrap()
+            .strip_prefix(&config.initial_sysroot)
+            .expect("Couldn’t determine initial relative libdir.")
+            .to_path_buf();
 
         let version = std::fs::read_to_string(src.join("src").join("version"))
             .expect("failed to read src/version");
@@ -383,11 +356,11 @@ impl Build {
         }
 
         let mut build = Build {
+            initial_lld,
+            initial_relative_libdir,
             initial_rustc: config.initial_rustc.clone(),
             initial_cargo: config.initial_cargo.clone(),
-            initial_lld,
-            initial_libdir,
-            initial_sysroot: initial_sysroot.into(),
+            initial_sysroot: config.initial_sysroot.clone(),
             local_rebuild: config.local_rebuild,
             fail_fast: config.cmd.fail_fast(),
             doc_tests: config.cmd.doc_tests(),