Partially revert "Temporarily fix rust-lang/rust#89658"

This reverts commit da9b7b2.

rust-lang/rust#89665

src/windows.rs

@@ -143,27 +143,11 @@ fn get_prefix(base: &BasePath) -> PrefixComponent<'_> {
 }
 
 fn push_separator(base: &mut BasePathBuf) {
-    // https://github.com/rust-lang/rust/issues/89658
-    /*
     base.replace_with(|mut base| {
         // Add a separator if necessary.
         base.push("");
         base
     });
-    */
-
-    const SEPARATOR: &str = "\\";
-
-    if let Some(Component::Prefix(prefix)) = base.components().next_back() {
-        if matches!(prefix.kind(), Prefix::Disk(_) | Prefix::VerbatimDisk(_)) {
-            return;
-        }
-    }
-    // This inefficient implementation must be used until the above issue is
-    // resolved.
-    if !base.0.to_string_lossy().ends_with(SEPARATOR) {
-        base.0.push(SEPARATOR);
-    }
 }
 
 pub(super) fn push(base: &mut BasePathBuf, initial_path: &Path) {