Blender Git Loki

Codesign: Harden check for archive being ready for sign

Seems like sometimes files are being only partially ready, which makes it so there
are unsigned files, failing to deliver fully signed bundle.

Now expected archive file size is stored into stamp file and is checked against
size of the archive file on another side.

There are some bare prints used for debugging, would need to switch it to a proper
logger (or to be removed).