Add symlink to cargo cache dir

This will improve performance on successive runs. Note that we store the cache on GitHub Actions, so it will make things much faster on CI.

Author: alexdewar

docs/build_old_docs.py

@@ -2,6 +2,7 @@
 #
 # A script to generate documentation for previous releases of MUSE2.
 
+import os
 import shutil
 import subprocess as sp
 import sys
@@ -20,6 +21,9 @@ def clone_repo_to(dest: Path):
     print("Making a copy of repo")
     sp.run(("git", "clone", REPO_ROOT, dest), check=True, capture_output=True)
 
+    # Add a symlink to cargo cache dir
+    os.symlink(REPO_ROOT / "target", dest / "target")
+
 
 def build_docs_for_release(release: str, repo_path: Path, outdir: Path) -> None:
     """Build documentation for a given release."""