Suppress the warning:
'fake_shared_weak_count' has virtual functions but non-virtual destructor [-Wnon-virtual-dtor]
The warning has been recently enabled [1], but the associated cleanup
missed this instance in Darwin code [2].
[1] 9c31e12609e1935eb84a2497ac08a49e3139859a
[2] d48f2d7c02743571075bb7812bb4c9e634e51ed1
clang-format not found in user's PATH; not linting file.