does reverting to the old build_miri_sysroot help?

Author: RalfJung

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

@@ -500,27 +500,46 @@ impl Miri {
     /// Run `cargo miri setup` for the given target, return where the Miri sysroot was put.
     pub fn build_miri_sysroot(
         builder: &Builder<'_>,
-        compiler: Compiler,
+        host_compiler: Compiler,
         target: TargetSelection,
     ) -> String {
-        let miri_sysroot = builder.out.join(compiler.host.triple).join("miri-sysroot");
-        let mut cargo = builder::Cargo::new(
+        let miri = builder.ensure(tool::Miri {
+            compiler: host_compiler,
+            target: host_compiler.host,
+            extra_features: Vec::new(),
+        });
+        let miri_sysroot = builder.out.join(host_compiler.host.triple).join("miri-sysroot");
+        let mut cargo = tool::prepare_tool_cargo(
             builder,
-            compiler,
-            Mode::Std,
-            SourceType::Submodule,
-            target,
-            "miri-setup",
+            host_compiler,
+            Mode::ToolRustc,
+            host_compiler.host,
+            "run",
+            "src/tools/miri/cargo-miri",
+            SourceType::InTree,
+            &[],
         );
+        cargo.add_rustc_lib_path(builder);
+        cargo.arg("--").arg("miri").arg("setup");
+        cargo.arg("--target").arg(target.rustc_target_arg());
 
         // Tell `cargo miri setup` where to find the sources.
         cargo.env("MIRI_LIB_SRC", builder.src.join("library"));
+        // Tell it where to find Miri.
+        cargo.env("MIRI", miri);
         // Tell it where to put the sysroot.
         cargo.env("MIRI_SYSROOT", &miri_sysroot);
+        // Debug things.
+        cargo.env("RUST_BACKTRACE", "1");
 
         let mut cargo = Command::from(cargo);
-        let _guard =
-            builder.msg(Kind::Build, compiler.stage, "miri sysroot", compiler.host, target);
+        let _guard = builder.msg(
+            Kind::Build,
+            host_compiler.stage + 1,
+            "miri sysroot",
+            host_compiler.host,
+            host_compiler.host,
+        );
         builder.run(&mut cargo);
 
         // # Determine where Miri put its sysroot.
@@ -593,7 +612,7 @@ impl Step for Miri {
 
         // We also need sysroots, for Miri and for the host (the latter for build scripts).
         // This is for the tests so everything is done with the target compiler.
-        let miri_sysroot = Miri::build_miri_sysroot(builder, target_compiler, target);
+        let miri_sysroot = Miri::build_miri_sysroot(builder, host_compiler, target);
         builder.ensure(compile::Std::new(target_compiler, host));
         let sysroot = builder.sysroot(target_compiler);