Recognize macOS 11 and later.
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=44605
https://bugs.php.net/bug.php?id=80393
https://github.com/php/php-src/commit/d016434ad33284dfaceb8d233351d34356566d7d
--- a/build/libtool.m4.orig
+++ b/build/libtool.m4
@@ -340,7 +340,7 @@ AC_DEFUN([_LT_REQUIRED_DARWIN_CHECKS],[
      _lt_dar_allow_undefined='${wl}-undefined ${wl}dynamic_lookup' ;;
    10.[[012]]*)
      _lt_dar_allow_undefined='${wl}-flat_namespace ${wl}-undefined ${wl}suppress' ;;
-   10.*)
+   *)
      _lt_dar_allow_undefined='${wl}-undefined ${wl}dynamic_lookup' ;;
       esac
     ;;
@@ -5799,7 +5799,7 @@ _LT_EOF
              10.[[012]])
                _LT_AC_TAGVAR(allow_undefined_flag, $1)='${wl}-flat_namespace ${wl}-undefined ${wl}suppress'
                ;;
-             10.*)
+             *)
                _LT_AC_TAGVAR(allow_undefined_flag, $1)='${wl}-undefined ${wl}dynamic_lookup'
                ;;
            esac