that nuget package contains the definitions for msbuild in order to build the PCF control (to get the correct output that after is packaged inside the solution)
Mono contains an implementation of msbuild but I don't know (as I didn't test) if it can work with PCF
Also if you are able to build the control, the packaging of the solution (using solutionpackager) afaik is only for windows (it is possible to manually package it but you will need to know exactly how the solution xml works)
Note that the things I wrote come from my experience, as this product is in preview maybe there are other ways to configure this on mac that I am not aware of, maybe the product team or other developers will reply to your question.
hope it helps