Do not do this to install llvm/clang on OSX
Installing llvm/clang on OSX 10.12.3 Sierra. Read the following if you want to take advantage of the five hours that I spent in this library.
Install XCode. This lets you use clang++ to compile c++ files.
After installing XCode, run the following in terminal:
brew install --with-clang --all-targets --rtti --universal --jit llvm
This will take about two hours. Find the llvm folder. In order to compile a c++ file, run the following, except replace ~/Desktop/example.cpp with the path to your file and /usr/local/Cellar/ with the path to your newly installed llvm folder.
clang++ ~/Desktop/example.cpp -std=c++11 -L /usr/local/Cellar/llvm/3.9.1/lib -lclang -o ~/Desktop/a.out
The -L flag shows clang where to find the llvm library that is necessary if you are trying to use any special clang functions. The -std flag tells the compiler what version of c++ to compile in (in this case, it is c++11). Older compilers do not support many features that are in c++11, which may be why this flag is necessary. I honestly do not know what -lclang does, but it makes the c++ file compile.
The -o ~/Desktop/a.out tells the compiler where to put the executable. The -o flag tells the compiler to create the file if it does not already exist.