Fix Windows test failures not being detected in CI (#36446)

Bug introduced in #35926 

Release Notes:

- N/A

crates/fs/src/fake_git_repo.rs

@@ -590,9 +590,9 @@ mod tests {
         assert_eq!(
             fs.files_with_contents(Path::new("")),
             [
-                (Path::new("/bar/baz").into(), b"qux".into()),
-                (Path::new("/foo/a").into(), b"lorem".into()),
-                (Path::new("/foo/b").into(), b"ipsum".into())
+                (Path::new(path!("/bar/baz")).into(), b"qux".into()),
+                (Path::new(path!("/foo/a")).into(), b"lorem".into()),
+                (Path::new(path!("/foo/b")).into(), b"ipsum".into())
             ]
         );
     }

crates/fs/src/fs.rs

@@ -1101,7 +1101,9 @@ impl FakeFsState {
     ) -> Option<(&mut FakeFsEntry, PathBuf)> {
         let canonical_path = self.canonicalize(target, follow_symlink)?;
 
-        let mut components = canonical_path.components();
+        let mut components = canonical_path
+            .components()
+            .skip_while(|component| matches!(component, Component::Prefix(_)));
         let Some(Component::RootDir) = components.next() else {
             panic!(
                 "the path {:?} was not canonicalized properly {:?}",