astral-sh/python-build-standalone 20210303 on GitHub

LLVM/Clang updated to 11.1.0.
preadv() and pwritev() are now disabled on x86_64-apple-darwin builds to restore compatibility with macOS < 11.0.
Windows static distributions now distribute libffi.lib and the _ctypes extension properly has a dependency on its annotated in PYTHON.json. This should fix issues generating a new library from object files when using metadata from PYTHON.json.
Windows distributions now have pythoncore annotated as linking against pathcch. This dependency was introduced in Python 3.9 and its previous lack of annotation in PYTHON.json resulted in missing symbols when linking pythoncore.