Setup: Fix .deb and .rpm installation package builds

Building [.deb](https://dl.photoprism.app/pkg/linux/deb/) and [.rpm](https://dl.photoprism.app/pkg/linux/rpm/) [installation package](https://dl.photoprism.app/pkg/linux/README.html) as an alternative simple .tar.gz archives failed after upgrading to the latest version of Ubuntu due to changes in Make that prevented the necessary environment variables from being exported.