Unrolled build for rust-lang#129194

Rollup merge of rust-lang#129194 - ChrisDenton:detect-src, r=Mark-Simulacrum

Fix bootstrap test `detect_src_and_out` on Windows

Fixes rust-lang#129188 by making sure it's properly testing the right path for the platform.

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

@@ -96,8 +96,8 @@ fn detect_src_and_out() {
     test(parse(""), None);
 
     {
-        let build_dir = if cfg!(windows) { Some("C:\\tmp") } else { Some("/tmp") };
-        test(parse("build.build-dir = \"/tmp\""), build_dir);
+        let build_dir = if cfg!(windows) { "C:\\tmp" } else { "/tmp" };
+        test(parse(&format!("build.build-dir = '{build_dir}'")), Some(build_dir));
     }
 }