Install 'data.table' R package with OpenMP on MacOS

Makevars

## R expects this file to be in its hidden config folder
# mkdir ~/.R
# touch ~/.R/Makevars

## Install 'OpenMP' using Homebrew in Terminal
# brew update && brew install libomp

## Include 'OpenMP' library with clang
HOMEBREW_PATH=/opt/homebrew
# 'openmp' was symlinked (package)
CPPFLAGS += -I$(HOMEBREW_PATH)/include
LDFLAGS += -L$(HOMEBREW_PATH)/lib
# 'openmp' wasn't symlinked (keg-only)
CPPFLAGS += -I$(HOMEBREW_PATH)/opt/libomp/include
LDFLAGS += -L$(HOMEBREW_PATH)/opt/libomp/lib

## Enable 'OpenMP' library with clang
CPPFLAGS += -Xclang -fopenmp
LDFLAGS += -lomp

## Install these packages to avoid compilation errors
# brew install xquartz
# brew install tcl-tk

## Install 'data.table' with R console
# remove.packages("data.table")
# install.packages("data.table", type = "source")

## Load 'data.table' with R console and test
# library("data.table")
# test.data.table()