Explicitly set compression ratio on resulting jar files

[Trial97]

This is a follow-up from the discussion in: #77 (comment)
@LexManos, hopefully, this is what you wanted.
In the installer, this is the only ZipOutputStream instance.
If this should not be done here but in a different repo, let me know. I will try to adjust, as I do not fully grasp what needs to be done.

[LexManos]

No, this is not the correct place. If you notice the task that you're working on doesn't actually check hashes.
The issue has alrwsyf been fixed and thus modern versions are not effected.
The issue is OLD already existing installers
So you would need to update all old installers to use the new installer tools/renamers where this issue is fixed.
Lucky for you we've had to fix the installer a few times for a few reasons. So I have a the core of the process already written https://github.com/MinecraftForge/InstallerRewriter