Make more intuitive error messages for packages with external dependencies

[jacobpwagner]

As an example case, if a Windows user tries to install all packages from GitHub using cytoverse_update(repo="github"), they will hit an error for RProtoBufLib because it requires them to install the protobuf library separately (https://github.com/RGLab/RProtoBufLib/blob/master/INSTALL), resulting in a message that is hard for most users to interpret:

** libs
*** arch - i386
mkdir -p "C:/Users/*****/Documents/R/win-library/4.0/00LOCK-RProtoBufLib/00new/RProtoBufLib/include"
cp -r /include/google "C:/Users/*****/Documents/R/win-library/4.0/00LOCK-RProtoBufLib/00new/RProtoBufLib/include"
cp: cannot stat '/include/google': No such file or directory
make: *** [Makevars.win:12: copying] Error 1
ERROR: compilation failed for package 'RProtoBufLib'

Ideally, we could check the external dependencies early on in cytoverse_update, but we could at least catch these well-established error messages and convert them to messages with instructions on how to solve the problem (or steering them to instructions like those at https://github.com/RGLab/RProtoBufLib/blob/master/INSTALL).

[jacobpwagner]

A few more examples of build issues to address:

With the change in Rtools4.0, the gsl headers now have to be manually added on Windows using the new pacman package manager: https://github.com/r-windows/docs/blob/master/rtools40.md#readme. In our case this shows up first in flowClust:

flowClust.h:1:10: fatal error: gsl/gsl_math.h: No such file or directory
 #include <gsl/gsl_math.h>

and can be solved from the following command in the Rtools bash utility:

pacman -S mingw-w64-{i686,x86_64}-gsl

Another example is the occasionally missing libxml2 dependency for CytoML: RGLab/CytoML#65.