Call build.sh script to setup the configure script when building from git source.

Similarly, call clean.sh for cleaning.

NOTE: There might be a more debian/dh way of doing that directly within
debian/rules, but this way makes use of the upstream scripts which is
probably easier to maintain.
Skip unnecessary patch when building for wheezy.

The amqp patch originally comes from the fact that this set of packaging
patches is derived from the collectd 5.4.0 package for jessie (Debian
testing), which has a newer version of librabbitmq-dev.