chore(CI): fix download packages error in build packages

.github/workflows/build_packages.yaml

@@ -268,6 +268,9 @@ jobs:
         if [ $PROFILE = "emqx" ];then
             broker="emqx-ce"
         fi
+        if [[ "$SYSTEM" =~ "raspbian*" ]];then
+            export ARCH="arm"
+        fi
 
         mkdir -p source/_upgrade_base
         cd source/_upgrade_base