build: standardize Dockerfile 'AS' syntax for multi-stage builds

- Change `FROM` statements to use uppercase `AS` for stage names in `Dockerfile`, `alpine.Dockerfile`, and `distroless.Dockerfile`.

Signed-off-by: 陳鈞 <[email protected]>

Dockerfile

@@ -6,7 +6,7 @@ ARG RELEASE=0
 ########################################
 # Final stage
 ########################################
-FROM alpine:3 as final
+FROM alpine:3 AS final
 
 # RUN mount cache for multi-arch: https://github.com/docker/buildx/issues/549#issuecomment-1788297892
 ARG TARGETARCH

alpine.Dockerfile

@@ -6,7 +6,7 @@ ARG RELEASE=0
 ########################################
 # Build stage
 ########################################
-FROM python:3.12-alpine as build
+FROM python:3.12-alpine AS build
 
 # RUN mount cache for multi-arch: https://github.com/docker/buildx/issues/549#issuecomment-1788297892
 ARG TARGETARCH
@@ -32,7 +32,7 @@ RUN --mount=type=cache,id=pip-$TARGETARCH$TARGETVARIANT,sharing=locked,target=/r
 ########################################
 # Final stage
 ########################################
-FROM python:3.12-alpine as final
+FROM python:3.12-alpine AS final
 
 RUN pip3.12 uninstall -y setuptools pip wheel && \
     rm -rf /root/.cache/pip

distroless.Dockerfile

@@ -5,7 +5,7 @@ ARG RELEASE=0
 ########################################
 # Build stage
 ########################################
-FROM python:3.12-bookworm as build
+FROM python:3.12-bookworm AS build
 
 # RUN mount cache for multi-arch: https://github.com/docker/buildx/issues/549#issuecomment-1788297892
 ARG TARGETARCH
@@ -35,7 +35,7 @@ RUN --mount=type=cache,id=pip-$TARGETARCH$TARGETVARIANT,sharing=locked,target=/r
 # Final stage
 # Distroless image use monty(1000) for non-root user
 ########################################
-FROM al3xos/python-distroless:3.12-debian12 as final
+FROM al3xos/python-distroless:3.12-debian12 AS final
 
 ARG UID=1000