zend call stack fixing stack limit for macOs arm64.

[devnexen]

8MB sounded a prudent size for older 10.9 macOs release, however with newer mac with arm64, it triggers a stack overflow.

[arnaud-lb]

Thank you! The code change looks good to me, but the new comments are redundant with the existing comment bellow them.

We could make the change self-explanatory by merging the code paths. For example (in pseudo code) :

if (pthread_main_np() && !arm64) {
    /* existing comment explaining the workaround for older OSX versions */
    max_size = 8 * 1024 * 1024;
} else {
    max_size = pthread_get_stacksize_np(pthread_self());
}

[divinity76]

#ifndef __aarch64__
	/* pthread_get_stacksize_np() returns a too low value for the main
	 * thread in OSX 10.9, 10.10:
	 * https://mail.openjdk.org/pipermail/hotspot-dev/2013-October/011353.html
	 */
	if (pthread_main_np()) {
		max_size = 8 * 1024 * 1024;
	} else
#endif
	max_size = pthread_get_stacksize_np(pthread_self());

should be slightly faster on modern macos

edit: fixed a logic error

[divinity76]

LGTM 👍