syntax error in Readme for PACKER_FLAGS

[grsiepka]

Hi, going thru your guide here and ran into small syntax error.

export PACKER_FLAGS="-var disk_format=raw cpu_type=host"

It looks like packer is expecting only one key=value pair for each -var. Any make build-proxmox-OS throws a Error 1 syntax error.

What worked for me was:

export PACKER_FLAGS="-var disk_format=raw -var cpu_type=host"

Thanks!