Auto merge of #142117 - jieyouxu:revert-rustc-sysroot-handling, r=<try>

[DO NOT MERGE] Experimental revert

r? ghost

try-job: aarch64-apple

Author: rust-bors[bot]

library/std/src/sys/process/unix/unix.rs

@@ -1,3 +1,4 @@
+// Force test comment
 #[cfg(target_os = "vxworks")]
 use libc::RTP_ID as pid_t;
 #[cfg(not(target_os = "vxworks"))]

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

@@ -2707,6 +2707,16 @@ impl Step for Crate {
                         .arg(builder.src.join("library/sysroot/Cargo.toml"));
                 } else {
                     compile::std_cargo(builder, target, compiler.stage, &mut cargo);
+                    // `std_cargo` actually does the wrong thing: it passes `--sysroot build/host/stage2`,
+                    // but we want to use the force-recompile std we just built in `build/host/stage2-test-sysroot`.
+                    // Override it.
+                    if builder.download_rustc() && compiler.stage > 0 {
+                        let sysroot = builder
+                            .out
+                            .join(compiler.host)
+                            .join(format!("stage{}-test-sysroot", compiler.stage));
+                        cargo.env("RUSTC_SYSROOT", sysroot);
+                    }
                 }
             }
             Mode::Rustc => {

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

@@ -66,6 +66,7 @@ use crate::{Command, GitInfo, OnceLock, TargetSelection, check_ci_llvm, helpers,
 #[rustfmt::skip] // We don't want rustfmt to oneline this list
 pub const RUSTC_IF_UNCHANGED_ALLOWED_PATHS: &[&str] = &[
     ":!library",
+    ":!src/bootstrap", // DO NOT MERGE, permit experimental bootstrap changes
     ":!src/tools",
     ":!src/librustdoc",
     ":!src/rustdoc-json-types",