Fix: Check for include directory before watching in local_runtime_repo

The local_runtime_repo rule was failing on macOS when the Python interpreter's metadata pointed to an include directory that did not exist. This change modifies the rule to check if the include directory exists and is a directory before attempting to watch it with `watch_tree`.

Author: google-labs-jules[bot]

python/private/local_runtime_repo.bzl

@@ -99,7 +99,14 @@ def _local_runtime_repo_impl(rctx):
     interpreter_path = info["base_executable"]
 
     # NOTE: Keep in sync with recursive glob in define_local_runtime_toolchain_impl
-    repo_utils.watch_tree(rctx, rctx.path(info["include"]))
+    include_path = rctx.path(info["include"])
+    if include_path.exists and include_path.is_dir:
+        repo_utils.watch_tree(rctx, include_path)
+    else:
+        # If the path doesn't exist or is not a directory, do not watch it.
+        # This handles the case where the include path specified in Python metadata
+        # is invalid or points to a file.
+        pass
 
     # The cc_library.includes values have to be non-absolute paths, otherwise
     # the toolchain will give an error. Work around this error by making them