Revision 776273

Temporary fix for http://jira.codehaus.org/browse/MASSEMBLY-409 by using a custom assembly descriptor.
This turned out to be more difficult than expected because the portals-pom-1.2 already configures the "project" predefined assemby and the maven-assembly-plugin
always merges descriptor configurations :(
"Fixed" by configuring a "dummy-does-not-exist" predefined descriptor (which then does override the "project") *and* configuring ignoreMissingDescriptor=true
Note: this still needs to be tested with mvn release:prepare -DdryRun=true, but to be able to do so this change needs to be committed first.