Hello there.
I had not anticipated to encounter this problem again so soon, but I did when I was installing yet another package on my own laptop.
ld: warning: directory not found for option '-L/usr/local/gfortran/lib/gcc/x86_64-apple-darwin15/6.
After a while of playing around, I’ll say the best way to use R with a Notebook-style interface on a server where you are no superuser would be using Anaconda, and then run R inside Anaconda to get whatever package you need.