Merge pull request kubernetes-sigs#447 from Trickybrain/fix-al-version

Fix: Add AL_VERSION default value in Makefile

Author: k8s-ci-robot

Makefile

@@ -35,6 +35,7 @@ OUTPUT_TYPE?=docker
 OS?=linux
 ARCH?=amd64
 OSVERSION?=amazon
+AL_VERSION?=al23
 
 ALL_OS?=linux
 ALL_ARCH_linux?=amd64 arm64