make alpine dockerfile arch-agnostic

.woodpecker/process_cran_updates.yaml

@@ -14,7 +14,7 @@ matrix:
 steps:
   - name: 'Processing Updates: (${PLATFORM})'
     secrets: [red_hat_dev_pw, aws_access_key_id, aws_secret_access_key, pgpass, git_ro_token, GITHUB_PAT]
-    image: docker.io/devxygmbh/arm-binaries-r-${PLATFORM}
+    image: docker.io/devxygmbh/arm64-binaries-r-${PLATFORM}
     pull: true
     # to ensure the PACKAGES upload step is being executed
     failure: ignore
@@ -25,7 +25,7 @@ steps:
       R_LIBS_USER: /mnt/cache/R-pkgs
       CCACHE_DIR: /mnt/cache/ccache
     volumes:
-      - arm-binaries-r-dep-cache-${PLATFORM}:/mnt/cache
+      - arm64-binaries-r-dep-cache-${PLATFORM}:/mnt/cache
     commands:
       # download latest package version (avoid having to rebuild image every time)
       - git clone https://pat-s:$$git_ro_token@git.devxy.io/devxy/arm64-r-binaries.git .