Optimize Alpine packaging workflow

scripts/apk/build.sh

@@ -19,6 +19,8 @@ if [[ "${builder_gid}" == "0" ]]; then
   builder_gid=1000
 fi
 
+image_name="${ALPINE_APK_BUILDER_IMAGE:-alpine-apk-builder:${alpine_version}-${builder_uid}-${builder_gid}}"
+
 cache_scope_from_remote() {
   local remote
   local path
@@ -63,7 +65,6 @@ run_for_arch() {
   local arch="$1"
   local subcommand="$2"
   local package_dir="$3"
-  local image_name
   local container_package_dir
   local package_name
   local cache_scope
@@ -73,19 +74,9 @@ run_for_arch() {
   apk_validate_package_dir "${package_dir}"
   package_name="$(apk_package_name "${package_dir}")"
   container_package_dir="$(apk_container_package_dir "${repo_root}" "${package_dir}")"
-  image_name="${ALPINE_APK_BUILDER_IMAGE:-alpine-apk-builder:${arch}}"
   cache_scope="${ALPINE_APK_CACHE_SCOPE:-$(cache_scope_from_remote)}"
   cache_prefix="${ALPINE_APK_CACHE_PREFIX:-alpine-apk}-${cache_scope}-${package_name}-${arch}"
 
-  docker build \
-    --platform "${build_platform}" \
-    --build-arg "ALPINE_VERSION=${alpine_version}" \
-    --build-arg "BUILDER_UID=${builder_uid}" \
-    --build-arg "BUILDER_GID=${builder_gid}" \
-    -f "${repo_root}/scripts/apk/Dockerfile" \
-    -t "${image_name}" \
-    "${repo_root}"
-
   docker_args=(--rm --platform "${build_platform}")
   if [[ -t 0 && -t 1 ]]; then
     docker_args+=(-it)
@@ -111,11 +102,33 @@ run_for_arch() {
     "${subcommand}"
 }
 
+build_builder_image() {
+  docker build \
+    --platform "${build_platform}" \
+    --build-arg "ALPINE_VERSION=${alpine_version}" \
+    --build-arg "BUILDER_UID=${builder_uid}" \
+    --build-arg "BUILDER_GID=${builder_gid}" \
+    -f "${repo_root}/scripts/apk/Dockerfile" \
+    -t "${image_name}" \
+    "${repo_root}"
+}
+
 mkdir -p \
   "${repo_root}/.cache/abuild" \
   "${repo_root}/.cache/apk-distfiles" \
   "${repo_root}/packages"
 
+case "${command_name}" in
+  build-all|build|checksum|lint|shell) ;;
+  *)
+    printf 'unknown command: %s\n' "${command_name}" >&2
+    printf 'usage: %s [build|build-all|checksum|lint|shell] [x86_64|aarch64]\n' "$0" >&2
+    exit 2
+    ;;
+esac
+
+build_builder_image
+
 case "${command_name}" in
   build-all)
     while IFS= read -r package_dir; do