bug#62975: 29.0.90; Forking processes on macOS has become very slow in Emacs 29

[Alan Third]

Check you have

    #define HAVE_POSIX_SPAWN 1

defined in config.h.

There's a much larger set of requirements to use posix_spawn at the top
of callproc.c, but I don't understand them.

If, for some reason, your system isn't using posix_spawn then it will be
using fork (Apple removed vfork) and yes, it will be as slow as Emacs 26.
-- 
Alan Third