first package i encountered is extra/nvidia-utils [0] (PKGBUILD can be retrieved via abs [1]) there you find
install -D -m644 LICENSE "${pkgdir}/usr/share/licenses/nvidia/LICENSE" ln -s nvidia "${pkgdir}/usr/share/licenses/nvidia-utils"
the same is done for a lot of lib32-packages in multilib. even if you still get a warning from namcap, this looks like a nice, clean and commonly accepted solution to me.
Ick. I'm surprised this is a common practice. It seems insane for one package to mess with a second package's files. Anyway, even similar packages may have distinct licenses. For example, JoKoT3 mentions that gnuplot-nox does not include the same set of dependencies as gnuplot. In theory, this means that the two packages could require different licenses.