reproducible archlinux: put /var/lib/schroot on tmpfs

TODO

@@ -301,7 +301,6 @@ The plan is to run a jenkins.d.o host, which is maintained by DSA, but we are ma
 ==== reproducible Arch Linux
 
 * describe archlinux setup…!
-* move /var/lib/schroot to /srv/workspace aka tmpfs
 * maintenance job:
 ** check for archlinux schroot sessions which should not be there and delete them. complain if that fails.
 ** properly clean schroot sessions, check on pb3…

hosts/profitbricks-build3-amd64/etc/rc.local

@@ -13,4 +13,10 @@
 
 echo "$(date -u) - system was rebooted" | mail -s "$(hostname -f) rebooted" root
 
+# keep schroot sessions on tmpfs
+[ -L /var/lib/schroot ] || echo "$(date -u) - /var/lib/schroot is not a link to /srv/workspace/varlibschroot/  as it should, please fix manually"
+cd /srv/workspace/varlibschroot || exit 1
+mkdir -p mount session union unpack
+mkdir -p union/overlay union/underlay
+
 exit 0