LLVM isn't so bad compared to the browsers. Relatively standard CMake build with mostly self contained c++ codebase and few third party dependencies. You don't need a crazy thread ripper workstation to do a build in reasonable time. A somewhat modern 8-16 core desktop CPU should be able to do it in 10-20 minutes or faster. Based on compilation benchmarks I have seen even some of 15 year old 4 core CPUs or 5year old mid/low tier mobile CPUs do it under hour.

Most importantly you need to pay attention to RAM usage, if necessary reducing parallelism so that it doesn't need to swap.