build: fix dockerfile typo

Author: viceice

Dockerfile

@@ -6,14 +6,14 @@ ARG DISTRO=focal
 #--------------------------------------
 # base images
 #--------------------------------------
-FROM ghcr.io/containerbase/ubuntu:20.04@sha256:8feb4d8ca5354def3d8fce243717141ce31e2c428701f6682bd2fafe15388214 as build-focal
-FROM ghcr.io/containerbase/ubuntu:22.04@sha256:c7eb020043d8fc2ae0793fb35a37bff1cf33f156d4d4b12ccc7f3ef8706c38b1 as build-jammy
+FROM ghcr.io/containerbase/ubuntu:20.04@sha256:8feb4d8ca5354def3d8fce243717141ce31e2c428701f6682bd2fafe15388214 AS build-focal
+FROM ghcr.io/containerbase/ubuntu:22.04@sha256:c7eb020043d8fc2ae0793fb35a37bff1cf33f156d4d4b12ccc7f3ef8706c38b1 AS build-jammy
 
 
 #--------------------------------------
 # builder images
 #--------------------------------------
-FROM build-${DISTRO} as builder
+FROM build-${DISTRO} AS builder
 
 
 ENTRYPOINT [ "dumb-init", "--", "builder.sh" ]