backend/backends: Add type annotations to CleanTrees
@@ -88,7 +88,7 @@ class CleanTrees:
Directories outputted by custom targets that have to be manually cleaned
because on Linux `ninja clean` only deletes empty directories.
'''
- def __init__(self, build_dir, trees):
+ def __init__(self, build_dir: str, trees: T.List[str]):
self.build_dir = build_dir
self.trees = trees
