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] 9c31e12609
[2] d48f2d7c02
Differential Revision: https://reviews.llvm.org/D94139
The xpc_connection_* APIs that we are intercepting are available
starting at macOS 10.7. This is old enough so that we don't need to
guard them.
llvm-svn: 369150
Julian Lettner