Set up infrastructure for custom build flavors #46
Description
E.g. with the ability to specify a list of PRs to include. We could either model this by automatically updating a fork of Mixxx or by dynamically applying the merges during CI.
A slightly adjacent idea would be the ability to build with different vcpkg environments, e.g. different Qt versions. Since this is generally non-trivial to perform automatically, we would likely have to pin a custom vcpkg revision for that.