is this the test you are refering to ? 
ac_cv_func_posix_spawn_file_actions_addchdir='no'
ac_cv_func_posix_spawn_file_actions_addchdir_np='yes'

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On Mon, May 5, 2025, 20:24 Eli Zaretskii <eliz@gnu.org> wrote:
> From: badli al rashid <theothernighttheotherday@gmail.com>
> Date: Mon, 5 May 2025 19:08:09 +0800
>
> error when running make
> callproc.c:1358:11: error: call to undeclared function 'posix_spawn_file_actions_addchdir_np'; ISO C99 and
> later do not support implicit function declarations [-Wimplicit-function-declaration]
>  1358 |   error = posix_spawn_file_actions_addchdir_np (actions, cwd);
>       |           ^
> 1 error generated.
> make[3]: *** [Makefile:444: callproc.o] Error 1
> make[3]: Leaving directory '/data/data/com.termux/files/home/emacs.git/src'
> make[2]: *** [Makefile:546: src] Error 2
> make[2]: Leaving directory '/data/data/com.termux/files/home/emacs.git'
> make[1]: *** [Makefile:1293: actual-bootstrap] Error 2
> make[1]: Leaving directory '/data/data/com.termux/files/home/emacs.git'
> make[1]: Entering directory '/data/data/com.termux/files/home/emacs.git'
> ***
> *** "make bootstrap" failed with exit status 2.

Please post the part of config.log where it tests for the functions
posix_spawn_file_actions_addchdir and
posix_spawn_file_actions_addchdir_np.