Propagate the RELEASE value from buildscripts to other repositories during build

The RELEASE variable resolution from https://github.com/cfengine/buildscripts/blob/master/build-scripts/package should be moved to a common place (https://github.com/cfengine/buildscripts/blob/master/build-scripts/functions ?) and an environment variable needs to be set in https://github.com/cfengine/buildscripts/blob/master/build-scripts/configure