Update build tags such that we can properly compile on all platforms (especially for packagers), and updated hack/PACKAGERS.md to mention the DOCKER_BUILDTAGS variable that will need to be set for binaries that might be used on AppArmor (such as Debian and especially Ubuntu)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)