Modernisation of the LHCb continuous integration build system

In the context of the LHCb upgrade for LHC Run 3, the experiment software builds and release infrastructure are being improved. In particular, we present the LHCb nightly builds pipelines which are modernised to provide a faster turnaround of the produced builds. The revamped system organises tasks of checkouts of the sources, builds and tests of the projects in LHCb software stacks on multiple architectures in a directed acyclic graph of dependencies, with the artifacts of each task cached and reused whenever possible, and distributes the jobs to the workers in the build farm. This work describes the implementation of the new system.