procutil: try and avoid angering CoreFoundation on macOS We've seen failures like this: objc[57662]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. objc[57662]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug. I think this is due to forking off some background processes during `hg update` or similar. I don't have any conclusive proof this is the fork() call that's to blame, but it's the most likely one since the regular `hg update` codepath uses the other fork() invocation (via workers) and we don't get this report from non-Google macOS users. Ugh. Differential Revision: https://phab.mercurial-scm.org/D7615