Include Cargo lockfiles in the prune xtask.

Author: adamreichold

x.py

@@ -121,10 +121,14 @@ def format_(args):
 
 def prune(args):
     shutil.rmtree("target", ignore_errors=True)
+    Path("Cargo.lock").unlink(missing_ok=True)
 
     for target_dir in gen_examples("target"):
         shutil.rmtree(target_dir, ignore_errors=True)
 
+    for lock_file in gen_examples("Cargo.lock"):
+        lock_file.unlink(missing_ok=True)
+
     for nox_dir in gen_examples(".nox"):
         shutil.rmtree(nox_dir, ignore_errors=True)