Issue with some macOS system (like macOS Catalina 10.15 from GitHub Actions)

[ArnaudBelcour]

With some macOS system (but not all), there is an issue with the multiprocessing part of emapper2gbk.

This leads to error like:

+[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.

For GitHub Actions, this lead to macOS job reaching time limit without completing.

The fix is to use the OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES before the python call, like:

OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES python test_emapper2gbk.py

Solution from: https://stackoverflow.com/a/52230415