feat: use multistage build

Dockerfile

@@ -1,4 +1,23 @@
-FROM rclone/rclone:1.59.0
+# for linux/amd64 platform
+FROM rclone/rclone:1.59.0 AS image-linux-amd64
+
+
+# for linux/arm64 platform
+FROM rclone/rclone:1.59.0 AS image-linux-arm64
+
+
+# for linux/arm/v7 platform
+FROM rclone/rclone:1.59.0 AS image-linux-armv7
+
+
+# for linux/arm/v6 platform
+FROM alpine:3.15 AS image-linux-armv6
+
+RUN apk add --no-cache rclone
+
+
+# main
+FROM image-${TARGETOS}-${TARGETARCH}${TARGETVARIANT}
 
 LABEL "repository"="https://github.com/ttionya/vaultwarden-backup" \
   "homepage"="https://github.com/ttionya/vaultwarden-backup" \