use eatmydata to speed up builds 8%

give a bit more credit where it's due

this version build different source packages for different architectures

which makes sense from one perspective: different arches (may) have different jdk build versions
but launchpad is not at all impressed with this approach, and it supersedes eg s390x with x64 builds
in short: launchpad will only keep 1 version per package + distro
we'll have to rewrite, and generate a single source package for all arches, and use Arch: any, and either switch on the arch during installation, or use debhelper's version prefixed versions. we'll see.