msbuild just deploy without build
You can define a configuration at solution level that tells msbuild which project has to be built/published/both. Obviously, to enable the "Publish" option, you have to setup also a publish profile for the project you want to deploy. But you should be able to simply uncheck the "Build" ones.
Here are some informations about solution configuration and how you can reference these configurations from your msbuild command:
So, in your case, i would do a configuration to build and one to deploy.