ZFile compress not work in overlaybd-merge

[BigVan]

What happened in your environment?

ubuntu 22.04

What did you expect to happen?

Overlaybd-merge should deflate the flattened layer by ZFile compressor. However it doesn't work by default, and it will lead to a crash when setting the option '--compress'

How can we reproduce it?

./overlaybd-merge --compress

What is the version of your Overlaybd?

a117098

What is your OS environment?

ubuntu 22.04

Are you willing to submit PRs to fix it?

• [X] Yes, I am willing to fix it.