Really disable some plugins

Previous we disabled some plugins that we want to keep around but can't port
yet by setting `build_by_default` to `false`. However, this isn't working on
many machines. I haven't figured out why, so instead lets just make their
meson.build files exit early.

Testing Done:
Ran the turtles on a machine that was still building these plugins.

Reviewed at https://reviews.imfreedom.org/r/3142/