meld:master commits

Reconfigure cache settings to accomodate the new ephemeral infrastructure. Remove rules to restrict CI to specific namespaces. Use the default WRK_DIR (by removing that setting) which is /Users/Shared/work. This wasn't possible before on the shared machine. It enables us to use a pre-built version of an already bootstrapped JHBuild, speeding up build times. No more need to force building everything from source.