images: set environment variable before upgrade
images: set environment variable before upgrade

Setting the environment variable after the upgrade "section" will not
have any effect in case caches are used. As we want the environment
variable to force a rebuild of the images we should use the environment
variable before the upgrade "section".

Fixes: 89bf923f952d ("image/builder: update Dockerfile from Dockerfile.builder")
Signed-off-by: André Martins <bc9800b9d52a24cce72a73dd528afed53f10e5fc@cilium.io>

tgraf/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tklauser/cilium,michi-covalent/cilium