Headless build of multi-project application with CrossCore

I'm trying to set up a continuous integration/testing pipeline for a multi-project application. I came across this question which partially answered how to do headless builds.

However, this doesn't quite help with my situation, as I have almost a dozen projects that need to be built and linked into a single program.

Using the '-project' option multiple times doesn't seem to work, nor does appending multiple paths after '-project'. Also, my projects are scattered across a working tree with other unrelated projects, so any import option that requires importing all projects under a common root is out of the question. 

Are there any other options that would suit my needs?