avoiding wayland and pkgbase

Hi, posted here because most here will be familiar with having to build
their own ports, and other things from source.

Is there a Correct way to completely avoid wayland [0]

Will we, after pkgbase becomes the default, still be able to build
world from downloaded sources? [1,2]

[0] with make.conf conditionals in the poudriere instance, for example. 
     Maybe even blacklisting it, if that doesn't break everything else.

[1] to tailor an install to its hardware, like cputype

[2] avoid building things that would never be used in its context
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