Source installation clang/clang++ error

Hi! I am trying to build PyTorch from source and am getting the following error:

CMake Error at /anaconda3/share/cmake-3.12/Modules/CMakeTestCXXCompiler.cmake:45 (message):
The C++ compiler

"/Library/Developer/CommandLineTools/usr/bin/clang++"

is not able to compile a simple test program.

I read through a lot of posts trying to figure out the issue and have tried downgrading my command line tools to no avail. I also read that AVX nor AVX2 is supported on mac and that might be the issue. But I’m not really sure what to do. Does anyone have suggestions? Thanks so much!