attempt parallel build

(cherry picked from commit 95a6ae15fdcda87e5cf47a0d96ce9a09b75fdb65)
(cherry picked from commit 920fea38158b610b1e70dc9a64c9292c933d4a28)
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 20da7a172c7b5b3ab6f65493cb2b1a5f2882d9be)
Add /run/shm -> /dev/shm symlink in debian/tmpfiles.d/debian.conf.

(cherry picked from commit bd4a35301aeb86578917c97809156efa14d5569f)