This also works for packing add-ons on your Mac after you made them.
Do not make an Automator Action to zip folders or use Finder's Archive option, Blockland can't read Mac ZipsStep 1: Download YemuZip:
http://www.yellowmug.com/yemuzip/Step 2: Drag the folder you want to pack into "Drop Files Here"
Step 3: Set the zip type to "PC Compatible"
Step 4: Compress and move the finished zip into your Add-Ons folder.
Done.