in pathconf, -1, not 0, means unsupported.. syncio presumably works, too.

[musl] / src / process / posix_spawn_file_actions_init.c

#include <spawn.h>

int posix_spawn_file_actions_init(posix_spawn_file_actions_t *fa)
{
        fa->__actions = 0;
        return 0;
}