resolve stage0 sysroot from rustc

Instead of manually navigating directories based on stage0 rustc, use `--print sysroot`
to get the sysroot directly. This also works when using the bootstrap `rustc` shim.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 3b8c3655b8d..d4b5a809215 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -1832,7 +1832,9 @@ impl Config {
                 .join(exe("rustc", config.build))
         };
 
-        config.initial_sysroot = config.initial_rustc.ancestors().nth(2).unwrap().into();
+        config.initial_sysroot = t!(PathBuf::from_str(
+            output(Command::new(&config.initial_rustc).args(["--print", "sysroot"])).trim()
+        ));
 
         config.initial_cargo_clippy = cargo_clippy;