chg: ``cached_cmd_on_image`` is now using ``/bin/sh`` rather than ``/bin/bash`` for supporting alpine images

bin/compose-core

@@ -366,7 +366,7 @@ cached_cmd_on_image() {
         return 0
     fi
     shift
-    out=$(docker run -i --rm --entrypoint /bin/bash "$image_id" -c "$*") || return 1
+    out=$(docker run -i --rm --entrypoint /bin/sh "$image_id" -c "$*") || return 1
     echo "$out" | tee "$cache_file"
 }
 export -f cached_cmd_on_image