24c6c35270
Pointed out in Issue #56432: the current reference models may not be quite friendly to open source projects. Their purpose is only illustrative - the expectation is that projects would train their own. To avoid unintentionally pulling such a model, made the URL cmake setting require explicit user setting. Differential Revision: https://reviews.llvm.org/D129342
See docs/CMake.html for instructions on how to build LLVM with CMake.