attempt parallel build

(cherry picked from commit 95a6ae15fdcda87e5cf47a0d96ce9a09b75fdb65)
(cherry picked from commit e24ff8b5940670f151c05b3cae9ed0a30d41eafd)
Remove pre-generated rules and unit files in debian/rules clean target.

These are generated with rootprefix=/usr and so has the wrong paths for Debian.

(cherry picked from commit 21aabc1183d9dccbbe50c9e292db01d07daf7c32)
Add /run/shm -> /dev/shm symlink in debian/tmpfiles.d/debian.conf

(cherry picked from commit d3c03a10e094560cb7239afcbbbb2797eb88d094)