Find the best way for compressing VHD files

[mzylowski]

During packer run we using:

deployment/oc-devel.vbox.pkr.hcl

Lines 63 to 65 in 1a8ca7b

	post-processor "compress" {
	output = "oc-devel.vhd.tar.gz"
	compression_level = 9

We can consider changing this to shell command a call 7z or something.

[mzylowski]

Command 7z a -t7z -m0=lzma -mx=9 -mfb=258 -md=32m -ms=on -mmt=on oc-devel-disk_9.0-beta.7z oc-devel-disk_9.0-beta.vhd compressed my image from 11GB VHD file to

Archive size: 3649711482 bytes (3481 MiB)

Size of tar.gz file after packer build was:

3826979237 oc-devel.vhd.tar.gz

So 3649 MiB.

My VHD image compressed by 7z was even bigger because I run a VM to generate OKAPI tiles (see #15).