Try to fix windows test failure

Cargo.toml

@@ -71,6 +71,7 @@ lddtree = "0.3.3"
 cc = "1.0.72"
 dunce = "1.0.2"
 normpath = "1.0.0"
+path-slash = "0.2.1"
 pep440_rs = { version = "0.3.6", features = ["serde"] }
 pep508_rs = { version = "0.2.1", features = ["serde"] }
 time = "0.3.17"

src/source_distribution.rs

@@ -6,6 +6,7 @@ use cargo_metadata::{Metadata, MetadataCommand};
 use fs_err as fs;
 use ignore::overrides::Override;
 use normpath::PathExt as _;
+use path_slash::PathExt as _;
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 use std::process::Command;
@@ -455,8 +456,16 @@ fn add_cargo_package_files_to_sdist(
             let relative_workspace_cargo_toml = relative_cargo_lock.with_file_name("Cargo.toml");
             let mut deps_to_keep = known_path_deps.clone();
             // Also need to the main Python binding crate
+            let workspace_root_slash = PathBuf::from(
+                workspace_root
+                    .to_path_buf()
+                    .into_std_path_buf()
+                    .to_slash()
+                    .unwrap()
+                    .as_ref(),
+            );
             let main_member_name = abs_manifest_dir
-                .strip_prefix(workspace_root)
+                .strip_prefix(workspace_root_slash)
                 .unwrap()
                 .to_str()
                 .unwrap()