build: update for creating alpha release tarballs

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@10205 ddefafc4-47db-0310-ae44-fa13212b10f2
build: update notes for building 1.9 series release tarballs on Debian 7

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@10206 ddefafc4-47db-0310-ae44-fa13212b10f2