diff --git a/.gitignore b/.gitignore
index b443fd58a1b..8012e93f6a9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,4 @@
-target
+/target
 **/*.rs.bk
 *.rlib
 *.o
@@ -11,9 +11,6 @@ perf.data.old
 /y.exe
 /y.pdb
 /build
-/build_sysroot/sysroot_src
-/build_sysroot/compiler-builtins
-/build_sysroot/rustc_version
 /dist
 /rust
 /download
diff --git a/build_system/build_sysroot.rs b/build_system/build_sysroot.rs
index cbbf09b9b97..711d4ccc55b 100644
--- a/build_system/build_sysroot.rs
+++ b/build_system/build_sysroot.rs
@@ -146,10 +146,11 @@ pub(crate) fn build_sysroot(
     }
 }
 
-// FIXME move to download/ or dist/
-pub(crate) static SYSROOT_RUSTC_VERSION: RelPath = RelPath::BUILD_SYSROOT.join("rustc_version");
-pub(crate) static SYSROOT_SRC: RelPath = RelPath::BUILD_SYSROOT.join("sysroot_src");
-static STANDARD_LIBRARY: CargoProject = CargoProject::new(&RelPath::BUILD_SYSROOT, "build_sysroot");
+pub(crate) static ORIG_BUILD_SYSROOT: RelPath = RelPath::SOURCE.join("build_sysroot");
+pub(crate) static BUILD_SYSROOT: RelPath = RelPath::DOWNLOAD.join("sysroot");
+pub(crate) static SYSROOT_RUSTC_VERSION: RelPath = BUILD_SYSROOT.join("rustc_version");
+pub(crate) static SYSROOT_SRC: RelPath = BUILD_SYSROOT.join("sysroot_src");
+static STANDARD_LIBRARY: CargoProject = CargoProject::new(&BUILD_SYSROOT, "build_sysroot");
 
 fn build_clif_sysroot_for_triple(
     dirs: &Dirs,
diff --git a/build_system/path.rs b/build_system/path.rs
index e93981f1d64..35ab6f111fe 100644
--- a/build_system/path.rs
+++ b/build_system/path.rs
@@ -42,7 +42,6 @@ impl RelPath {
     pub(crate) const DIST: RelPath = RelPath::Base(PathBase::Dist);
 
     pub(crate) const SCRIPTS: RelPath = RelPath::SOURCE.join("scripts");
-    pub(crate) const BUILD_SYSROOT: RelPath = RelPath::SOURCE.join("build_sysroot");
     pub(crate) const PATCHES: RelPath = RelPath::SOURCE.join("patches");
 
     pub(crate) const fn join(&'static self, suffix: &'static str) -> RelPath {
diff --git a/build_system/prepare.rs b/build_system/prepare.rs
index 8ac67e8f942..f9ef29849eb 100644
--- a/build_system/prepare.rs
+++ b/build_system/prepare.rs
@@ -3,9 +3,11 @@
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
-use super::build_sysroot::{SYSROOT_RUSTC_VERSION, SYSROOT_SRC};
+use crate::build_system::rustc_info::get_default_sysroot;
+
+use super::build_sysroot::{BUILD_SYSROOT, ORIG_BUILD_SYSROOT, SYSROOT_RUSTC_VERSION, SYSROOT_SRC};
 use super::path::{Dirs, RelPath};
-use super::rustc_info::{get_file_name, get_rustc_path, get_rustc_version};
+use super::rustc_info::{get_file_name, get_rustc_version};
 use super::utils::{copy_dir_recursively, spawn_and_wait, Compiler};
 
 pub(crate) fn prepare(dirs: &Dirs) {
@@ -49,27 +51,27 @@ pub(crate) fn prepare(dirs: &Dirs) {
 }
 
 fn prepare_sysroot(dirs: &Dirs) {
-    let rustc_path = get_rustc_path();
-    let sysroot_src_orig = rustc_path.parent().unwrap().join("../lib/rustlib/src/rust");
-    let sysroot_src = SYSROOT_SRC;
-
+    let sysroot_src_orig = get_default_sysroot().join("lib/rustlib/src/rust");
     assert!(sysroot_src_orig.exists());
 
-    sysroot_src.ensure_fresh(dirs);
-    fs::create_dir_all(sysroot_src.to_path(dirs).join("library")).unwrap();
     eprintln!("[COPY] sysroot src");
+
+    BUILD_SYSROOT.ensure_fresh(dirs);
+    copy_dir_recursively(&ORIG_BUILD_SYSROOT.to_path(dirs), &BUILD_SYSROOT.to_path(dirs));
+
+    fs::create_dir_all(SYSROOT_SRC.to_path(dirs).join("library")).unwrap();
     copy_dir_recursively(
         &sysroot_src_orig.join("library"),
-        &sysroot_src.to_path(dirs).join("library"),
+        &SYSROOT_SRC.to_path(dirs).join("library"),
     );
 
     let rustc_version = get_rustc_version();
     fs::write(SYSROOT_RUSTC_VERSION.to_path(dirs), &rustc_version).unwrap();
 
     eprintln!("[GIT] init");
-    init_git_repo(&sysroot_src.to_path(dirs));
+    init_git_repo(&SYSROOT_SRC.to_path(dirs));
 
-    apply_patches(dirs, "sysroot", &sysroot_src.to_path(dirs));
+    apply_patches(dirs, "sysroot", &SYSROOT_SRC.to_path(dirs));
 }
 
 pub(crate) struct GitRepo {
diff --git a/build_system/tests.rs b/build_system/tests.rs
index 37c35106af6..bc112910ce6 100644
--- a/build_system/tests.rs
+++ b/build_system/tests.rs
@@ -1,3 +1,5 @@
+use crate::build_system::build_sysroot::SYSROOT_SRC;
+
 use super::build_sysroot;
 use super::config;
 use super::path::{Dirs, RelPath};
@@ -262,7 +264,7 @@ const fn new(config: &'static str, func: &'static dyn Fn(&TestRunner)) -> Self {
     CargoProject::new(&SIMPLE_RAYTRACER_REPO.source_dir(), "simple_raytracer");
 
 static LIBCORE_TESTS: CargoProject =
-    CargoProject::new(&RelPath::BUILD_SYSROOT.join("sysroot_src/library/core/tests"), "core_tests");
+    CargoProject::new(&SYSROOT_SRC.join("library/core/tests"), "core_tests");
 
 const EXTENDED_SYSROOT_SUITE: &[TestCase] = &[
     TestCase::new("test.rust-random/rand", &|runner| {
diff --git a/clean_all.sh b/clean_all.sh
index 1760e5836ec..34cb081e375 100755
--- a/clean_all.sh
+++ b/clean_all.sh
@@ -1,10 +1,9 @@
 #!/usr/bin/env bash
 set -e
 
-rm -rf build_sysroot/{sysroot_src/,target/,compiler-builtins/,rustc_version}
-rm -rf target/ build/ dist/ perf.data{,.old} y.bin
-rm -rf download/
+rm -rf target/ download/ build/ dist/ y.bin y.exe
 
 # Kept for now in case someone updates their checkout of cg_clif before running clean_all.sh
 # FIXME remove at some point in the future
 rm -rf rand/ regex/ simple-raytracer/ portable-simd/ abi-checker/ abi-cafe/
+rm -rf build_sysroot/{sysroot_src/,target/,compiler-builtins/,rustc_version}
diff --git a/scripts/rustup.sh b/scripts/rustup.sh
index bc4c06ed7d2..6111c205444 100755
--- a/scripts/rustup.sh
+++ b/scripts/rustup.sh
@@ -17,10 +17,10 @@ case $1 in
         done
 
         ./clean_all.sh
-        ./y.rs prepare
 
         (cd build_sysroot && cargo update)
 
+        ./y.rs prepare
         ;;
     "commit")
         git add rust-toolchain build_sysroot/Cargo.lock
diff --git a/scripts/setup_rust_fork.sh b/scripts/setup_rust_fork.sh
index 6c64b7de7da..88bc6445503 100644
--- a/scripts/setup_rust_fork.sh
+++ b/scripts/setup_rust_fork.sh
@@ -51,7 +51,7 @@ popd
 # FIXME remove once inline asm is fully supported
 export RUSTFLAGS="$RUSTFLAGS --cfg=rustix_use_libc"
 
-export CFG_VIRTUAL_RUST_SOURCE_BASE_DIR="$(cd build_sysroot/sysroot_src; pwd)"
+export CFG_VIRTUAL_RUST_SOURCE_BASE_DIR="$(cd download/sysroot/sysroot_src; pwd)"
 
 # Allow the testsuite to use llvm tools
 host_triple=$(rustc -vV | grep host | cut -d: -f2 | tr -d " ")