reproducible Debian and jenkins.debian.net in general: seems we're good for buster

Signed-off-by: Holger Levsen <holger@layer-acht.org>

README

@@ -136,6 +136,8 @@ Installation tests inside chroot environments.
 * The (current) purpose of https://tests.reproducible-builds.org is to show the potential of reproducible builds for Debian - and six other projects currently. This is research, showing what could (and should) be done... check https://wiki.debian.org/ReproducibleBuilds for the real status of the project for Debian!
 
 * For Debian, four suites, 'stretch', 'buster', 'unstable' and 'experimental', are tested on four architectures: 'amd64', 'i386', 'arm64' and 'armhf'. The tests are done using 'pbuilder' through several concurrent workers: 40 for 'amd64', 24 for 'i386', 32 for 'arm64' and 51 for 'armhf', which are each constantly testing packages and saving the results of these tests. There's a single link:https://anonscm.debian.org/git/qa/jenkins.debian.net.git/tree/bin/reproducible_build_service.sh[systemd service] starting all of these link:https://anonscm.debian.org/git/qa/jenkins.debian.net.git/tree/bin/reproducible_worker.sh[workers] which in turn launch the actual link:https://anonscm.debian.org/git/qa/jenkins.debian.net.git/tree/bin/reproducible_build.sh[build script]. (So the actual builds and tests are happening outside the jenkins service.)
+** To shutdown all the workers use:  `sudo systemctl stop reproducible_build@startup.service ; /srv/jenkins/bin/reproducible_cleanup_nodes.sh`
+** To start all the workers use: `sudo systemctl start reproducible_build@startup.service`
 
 * These builds on remote nodes run on very different hardware:
 ** for 'amd64' we are using four virtual machines, profitbricks-build(1+5+11+15)-amd64, which have 15 or 16 cores and 48gb ram each. These nodes are sponsored by link:https://jenkins.debian.net/userContent/thanks.html[Profitbricks].

TODO4buster.txt

-special deployement needed for this:
-------------------------------------
- $ sudo systemctl stop reproducible_build@startup.service >> document this in README or INSTALL
-
-changes not yet prepared in git
--------------------------------
-finally, remove this file again.