refactor: use Path::push to construct remap-path-prefix

It creates paths with correct separators for different systems.

Author: weihanglo

src/cargo/core/compiler/mod.rs

@@ -1313,7 +1313,11 @@ fn sysroot_remap(build_runner: &BuildRunner<'_, '_>, unit: &Unit) -> OsString {
     let sysroot = &build_runner.bcx.target_data.info(unit.kind).sysroot;
     let mut remap = OsString::from("--remap-path-prefix=");
     remap.push(sysroot);
-    remap.push("/lib/rustlib/src/rust"); // See also `detect_sysroot_src_path()`.
+    // See also `detect_sysroot_src_path()`
+    remap.push("lib");
+    remap.push("rustlib");
+    remap.push("src");
+    remap.push("rust");
     remap.push("=");
     remap.push("/rustc/");
     if let Some(commit_hash) = build_runner.bcx.rustc().commit_hash.as_ref() {