local_crate_repository: symlink to realpath on Windows

Bazel ≥ 9.0.1 replants workspace symlinks as relative `..\_main\...`
paths that resolve at the output_base but not in the action execroot's
`external/` (there is no `external/_main`). Using `entry.realpath`
on Windows ensures each action sees the source files directly.

Author: walter-zeromatter

rs/private/crate_repository.bzl

@@ -89,8 +89,13 @@ def _local_crate_repository_impl(rctx):
     if not root.exists:
         fail("crate path %s does not exist" % rctx.attr.path)
 
+    # On Windows, Bazel >= 9.0.1 replants workspace symlinks as relative
+    # `..\_main\...` paths that resolve at the output_base but not in the
+    # action execroot's `external/` (there is no `external/_main`). Symlink
+    # to the realpath instead so each action sees the source files directly.
+    is_windows = rctx.os.name.lower().startswith("windows")
     for entry in root.readdir():
-        rctx.symlink(entry, entry.basename)
+        rctx.symlink(entry.realpath if is_windows else entry, entry.basename)
 
     patch(rctx)
 
@@ -99,7 +104,7 @@ def _local_crate_repository_impl(rctx):
     rctx.file("BUILD.bazel", _generate_build_file(rctx, cargo_toml))
 
     return rctx.repo_metadata(
-        reproducible = bazel_features.external_deps.repo_rules_relativize_symlinks,
+        reproducible = bazel_features.external_deps.repo_rules_relativize_symlinks and not is_windows,
     )
 
 local_crate_repository = repository_rule(