Recognize macOS 11 and later.
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=44605
--- libffi/configure.orig	2022-01-12 14:49:47.000000000 -0600
+++ libffi/configure	2022-01-12 14:58:38.000000000 -0600
@@ -8302,7 +8302,7 @@
              10.[012])
                allow_undefined_flag='${wl}-flat_namespace ${wl}-undefined ${wl}suppress'
                ;;
-             10.*)
+             *)
                allow_undefined_flag='${wl}-undefined ${wl}dynamic_lookup'
                ;;
            esac
@@ -11288,7 +11288,7 @@
              10.[012])
                allow_undefined_flag_CXX='${wl}-flat_namespace ${wl}-undefined ${wl}suppress'
                ;;
-             10.*)
+             *)
                allow_undefined_flag_CXX='${wl}-undefined ${wl}dynamic_lookup'
                ;;
            esac
@@ -15365,7 +15365,7 @@
              10.[012])
                allow_undefined_flag_F77='${wl}-flat_namespace ${wl}-undefined ${wl}suppress'
                ;;
-             10.*)
+             *)
                allow_undefined_flag_F77='${wl}-undefined ${wl}dynamic_lookup'
                ;;
            esac
@@ -17842,7 +17842,7 @@
              10.[012])
                allow_undefined_flag_GCJ='${wl}-flat_namespace ${wl}-undefined ${wl}suppress'
                ;;
-             10.*)
+             *)
                allow_undefined_flag_GCJ='${wl}-undefined ${wl}dynamic_lookup'
                ;;
            esac