build: fix multi platform mistake

Author: autumnjolitz

.github/workflows/main.yml

@@ -48,9 +48,6 @@ jobs:
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
-      -
-        name: Set up containerd
-        uses: crazy-max/ghaction-setup-containerd@v2
 
       -
         id: image_env

Dockerfile.alpine

@@ -5,7 +5,7 @@ ARG PYTHON_VERSION=3.12
 ARG SOURCE_IMAGE=docker.io/python:${PYTHON_VERSION}-alpine${ALPINE_VERSION}
 ARG BASE_IMAGE_DIGEST
 
-FROM --platform=$BUILDPLATFORM ${SOURCE_IMAGE}@${BASE_IMAGE_DIGEST} AS buildroot
+FROM --platform=$TARGETPLATFORM ${SOURCE_IMAGE}@${BASE_IMAGE_DIGEST} AS buildroot
 ARG PYTHON_VERSION=3.12
 
 ARG BUILD_ROOT='/dest'

examples/simple-flask/Dockerfile

@@ -1,7 +1,7 @@
 #syntax=docker/dockerfile:1
 ARG SOURCE_IMAGE=autumnjolitz/distroless-python:3.12-alpine3.20
 
-FROM --platform=$BUILDPLATFORM ${SOURCE_IMAGE}-buildroot AS buildroot
+FROM --platform=$TARGETPLATFORM ${SOURCE_IMAGE}-buildroot AS buildroot
 
 ADD requirements.txt .
 
@@ -11,7 +11,7 @@ RUN python -m pip install \
         -r requirements.txt
 
 ARG SOURCE_IMAGE=autumnjolitz/distroless-python:3.12-alpine3.20
-FROM --platform=$BUILDPLATFORM ${SOURCE_IMAGE}
+FROM --platform=$TARGETPLATFORM ${SOURCE_IMAGE}
 
 EXPOSE 8080