export a flag to disable objc fork safety.

[mediocretes]

This is required in order to get forking to work properly in the docraptor tests. as things labeled 'unsafe' go, it is fairly safe. We have seen this before and this was the solution then, too. Read more: https://stackoverflow.com/questions/52671926/rails-may-have-been-in-progress-in-another-thread-when-fork-was-called

[fzhunt]

This is the line that the internet says we need, looks good to me.

[tonydewan]

I'm not currently running the common files, trying to run lean. I'm running with this for a bit:

set_objc_fork_safety() {
  if [ "$(pwd | xargs basename)" = "doc_raptor" ]; then
    export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
  else
    unset OBJC_DISABLE_INITIALIZE_FORK_SAFETY
  fi
}

autoload -U add-zsh-hook
add-zsh-hook chpwd set_objc_fork_safety