Install xgboost r-pkg on Mac OS 10.14 with openMP

install-xgboost.sh

export C_INCLUDE_PATH=$(/usr/local/clang-7/bin/llvm-config --includedir)
export CPLUS_INCLUDE_PATH=$(/usr/local/clang-7/bin/llvm-config --includedir)
export LIBRARY_PATH=$(/usr/local/clang-7/bin/llvm-config --libdir)

git clone --recursive https://github.com/dmlc/xgboost
cd xgboost
cp make/config.mk config.mk
vi config.mk
# make edits such that
# export CC = /usr/local/clang-7/bin/clang
# export CXX = /usr/local/clang-7/bin/clang++

make
rm -r build
mkdir build
cd build

CC=/usr/local/clang-7/bin/clang CXX=/usr/local/clang-7/bin/clang++ cmake -DR_LIB=ON ..
make
make install