fix: ignore errors when cleaning up runtime cache (#2859)

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### QC
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* [x] The PR contains a test case for the changes or the changes are
already covered by an existing test case.
* [x] The documentation (`docs/`) is updated to reflect the changes or
this is not necessary (e.g. if the change does neither modify the
language nor the behavior or functionalities of Snakemake).

snakemake/sourcecache.py

@@ -353,7 +353,9 @@ def __init__(self, cache_path: Path, runtime_cache_path: Path = None):
         if runtime_cache_path is None:
             runtime_cache_parent = self.cache_path / "runtime-cache"
             os.makedirs(runtime_cache_parent, exist_ok=True)
-            self.runtime_cache = tempfile.TemporaryDirectory(dir=runtime_cache_parent)
+            self.runtime_cache = tempfile.TemporaryDirectory(
+                dir=runtime_cache_parent, ignore_cleanup_errors=True
+            )
             self._runtime_cache_path = None
         else:
             self._runtime_cache_path = runtime_cache_path