You'll want to extract your database schemas into dacpac files (assuming that you're using SSDT SQLProj files and not the old DBProj files for your projects). You can do this through SSMS or through the SQLPackage command line. Once extracted, put them in some place that all of the projects can hit (and preferably that's still under source control so everyone else can reference it). Add those dacpac files to your projects as database references, probably without the option to use a variable for the DB Name.
I've written up adding database reference on my blog here: http://schottsql.blogspot.com/2012/10/ssdt-external-database-references.html
One additional note - if you're building new databases from these projects, you'll likely need to go through several passes. Turn off the option to run as a transaction and to fail when there's an error so some objects will be created, repeat as needed until all objects are created. I used a variable in my projects called "DeployType" and set up my pre and post deploy scripts to handle a DeployType of "New" differently so it wouldn't attempt to populate/update any data for "New" builds.