updates/requirements/*/build.xml scripts should include pack.gz artifacts (using p2.process.artifacts pack="true") to make resolving multiple.target faster

All ant scripts (updates/requirements/*/build.xml) used to mirror 3rd party reqs from Eclipse.org and other places should be updated to generate .pack.gz artifacts too.

<p2.process.artifacts pack="true" repositoryPath="file:/${repoDirLocation}" />

Refs:

• http://git.eclipse.org/c/platform/eclipse.platform.releng.eclipsebuilder.git/plain/scripts/repoRelated/process-artifacts.xml
• http://help.eclipse.org/juno/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Fguide%2Fp2_repositorytasks.htm&cp=2_0_20_3_3