PyPy3 build missing header entry 'Py_UNUSED'

It looks like the PyPy3 build for Ubuntu 16.04 (PyPy 7.1.1-beta0 with GCC 6.2.0 20160901) [1] doesn’t have Py_UNUSED from the cpyext headers defined.[2]

Can this be corrected (maybe while moving to PyPy 7.3.2)?

[1] https://storage.googleapis.com/travis-ci-language-archives/python/binaries/ubuntu/16.04/x86_64/pypy3.tar.bz2

[2] https://foss.heptapod.net/pypy/pypy/-/issues/3245