Move configure-time checks for OSX/XCode compatibility to a separate macro #25208
Description
Just a little further configure.ac cleanup. This is a big chunk of code that deserves to be centralized in one place if/when further updates to it are needed.
Depends on #25118
CC: @dimpase
Component: build: configure
Author: Erik Bray
Branch/Commit: 13619ff
Reviewer: Frédéric Chapoton
Issue created by migration from https://trac.sagemath.org/ticket/25208