Adjust CPU name as arm64-darwin

config.sub replaces arm64 with aarch64.

configure.ac

@@ -80,6 +80,14 @@ dnl checks for alternative programs
 AC_CANONICAL_BUILD
 AC_CANONICAL_HOST
 AC_CANONICAL_TARGET
+AS_CASE(["$target_cpu-$target_os"],
+    [aarch64-darwin*], [
+        target_cpu=arm64
+        AS_CASE(["$target_vendor"], [unknown], [target_vendor=apple])
+        target="$target_cpu-$target_vendor-$target_os"
+        target_alias="$target_cpu-$target_os"
+    ])
+
 AC_ARG_PROGRAM
 RUBY_RM_RECURSIVE
 AC_ARG_WITH(gcc,