If two projects depend on each other through referenced projects, a build error will be generated, since circular build references is not permissible by design.
If multiple projects needs to be built at the same time, a single referenced project can be used for the first dependency, and the second project can set the 'Projects referencing this build configuration' flag, so that building the first or second project will cause the other one to be built automatically. This also applies to referenced build configuration for single or multiple projects.
For example, if two different build configurations (Debug and Release) of a single project need to be built no matter which one of the two build configuration is active, the 'Debug' build configuration can reference the 'Release' build configuration in the 'References' tab, and the 'Release' build configuration can have its Projects referencing this build configuration' flag set to 'true', so that both the 'Debug' and 'Release' build configurations will be built together, no matter which one is active.