I did find an example of the local file which I copied over and uncomented the line you mentioned. This is what my local file looks like. Are there other lines I should comment out? As it is, I still got the same error:
# To use this template, make a copy from make/local.example to make/local and uncomment options as n# To use this template, make a copy from make/local.example to make/local and uncomment options as needed.
# Be sure to run `make clean-all` before compiling a model to make sure everything gets rebuilt.
# Change the C++ compiler
# CXX=clang++
# Enable threading
STAN_THREADS=true
# Enable the MPI backend (requires also setting (replace gcc with clang on Mac)
# STAN_MPI=true
# CXX=mpicxx
# TBB_CXX_TYPE=gcc
# Enable the OpenCL backend
# STAN_OPENCL=true
# Add flags that are forwarded to the Stan-to-C++ compiler (stanc3).
# This example enables pedantic mode
# STANCFLAGS+= --warn-pedantic
# Enable C++ compiler and linker optimization recommended by Stan developers.
# Can significantly slow down compilation.
# STAN_CPP_OPTIMS=true
# Remove range checks from the model for faster runtime. Use this flag with caution
# and only once the indexing has been validated. In case of any unexpected behavior
# remove the flag for easier debugging.
# STAN_NO_RANGE_CHECKS=true
# Adding other arbitrary C++ compiler flags
# CXXFLAGS+= -funroll-loops
~