Update alpine-mainline.yml

Author: alessfg

.github/workflows/alpine-mainline.yml

@@ -51,7 +51,7 @@ jobs:
         id: build
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
-          platforms: linux/amd64
+          platforms: linux/amd64, linux/arm64
           context: "{{ defaultContext }}:mainline/alpine-slim"
           tags: nginx-unprivileged:alpine-slim
           push: false
@@ -111,7 +111,7 @@ jobs:
         id: build
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
-          platforms: linux/amd64
+          platforms: linux/amd64, linux/arm64
           context: "{{ defaultContext }}:mainline/alpine"
           tags: localhost:5000/nginx-unprivileged:alpine
           build-args: IMAGE=localhost:5000/nginx-unprivileged:alpine-slim