RStan and map_rect

Looks like I got it working. I think my mistake was having

CXX14FLAGS = -O3 -march=native -mtune=native

instead of

CXX14FLAGS += -O3 -march=native -mtune=native

My new Makevars, which works is:

CXX14 = icc
CXX14FLAGS = -DSTAN_THREADS
CXX14FLAGS += -O3 -march=native -mtune=native
CXX14FLAGS += -fPIC

Thanks again for all the help!