bug#46638: 28.0.50; Hang on macOS with nativecomp in regex-emacs

[Eli Zaretskii]

> From: Aaron Jensen <aaronjensen@gmail.com>
> Date: Fri, 19 Feb 2021 09:58:22 -0600
> 
>     2457 Thread_11734453   DispatchQueue_1: com.apple.main-thread  (serial)
>     + 2457 F70726f636573732d66696c65_process_file_0  (in 
> simple-fab5b0cf-4ca11a8e.eln) + 800  [0x10b3479f0]
>     +   2457 Fapply  (in emacs) + 625  [0x107067751]  eval.c:2636
>     +     2457 Ffuncall  (in emacs) + 640  [0x107067a10]  eval.c:3006
>     +       2457 funcall_subr  (in emacs) + 181  [0x1070682e5]  eval.c:0
>     +         2457 Fcall_process  (in emacs) + 175  [0x1070bd8ff]  
> callproc.c:285
>     +           2457 call_process  (in emacs) + 2109  [0x1070be1dd]  
> callproc.c:609
>     +             2457 re_match_2_internal  (in emacs) + 154  [0x1070350ea]  
> regex-emacs.c:3964

callproc.c:609 doesn't call re_match_2_internal, it calls
emacs_spawn.  What am I missing here?