Prereqs for installing packages with `devtools::install_github()`

I've never had an issue installing GitHub packages until recently, when I had trouble with two packages, including, which have C++ code. I solved the issue by following the instructions here to install XCode Command Line Tools on MacOS Mojave (R version 3.6.1)

My question is the following: are there general instructions that I can provide to students on what they need to use devtools::install_github()? Is the clang7 R binary or GNU Fortran 6.1 -- or anything else -- necessary for the packages with code that needs to be compiled? I did not install anything besides XCode CLI to install santoku, which was surprising, since this note from CRAN suggests otherwise:

"Important: this release uses Clang 7.0.0 and GNU Fortran 6.1, neither of which is supplied by Apple. If you wish to compile R packages from sources, you will need to download and install those tools - see the tools directory."

Thanks in advance for shedding light on this topic.