[Rd] rgl install for R 3.7

[Koenker, Roger W]

I’ve installed R 3.7.0 on a new laptop running macos 10.14.5 and have managed to get most of my usual packages
to compile from source with a ~/.R/Makevars file that looks like this:

CC=/usr/local/clang8/bin/clang
CXX=/usr/local/clang8/bin/clang++ 
LDFLAGS=-L/usr/local/clang8/lib 
CPPFLAGS=-I/usr/local/clang8/include -I/opt/X11/include/freetype2
FC=/usr/local/gfortran/bin/gfortran
FLIBS=-L/usr/local/gfortran/lib -lgfortran

As usual, the last challenge seems to be to get rgl installed.  Compilation _seems_ to go 
smoothly, but I now see:


Error in dyn.load(file, DLLpath = DLLpath, ...) :
  unable to load shared object '/Library/Frameworks/R.framework/Versions/3.7/Resources/library/00LOCK-rgl/00new/rgl/libs/rgl.so':
  dlopen(/Library/Frameworks/R.framework/Versions/3.7/Resources/library/00LOCK-rgl/00new/rgl/libs/rgl.so, 6): Symbol not found: _FT_Attach_File
  Referenced from: /Library/Frameworks/R.framework/Versions/3.7/Resources/library/00LOCK-rgl/00new/rgl/libs/rgl.so


There is a comment somewhat after this about rgl requiring XQuartz, but I have  XQuartz 2.7.11 so I don’t
think that this is the problem.  Apparently, there is still a freetype problem, however I’m out of my depth at this
point.   Any suggestions would be most welcome.

Roger Koenker
Honorary Professor
Department of Economics, UCL
London  WC1H 0AX.