To upgrade clang-format to use the v4 toolchain, we will need to support developers on OSX by making a clang-format 12.0.1 binary distribution available. We have several options for doing this:
1. Tell users to install the llvm@12 homebrew formula, which includes clang-format
2. Create a homebrew tap with clang-format formulae available for versions corresponding to mongodbtoolchain (we would modify this forumla)
3. Manually build and upload static clang-format binaries to the boxes.10gen.com bucket (requires S3 permissions and someone on the team to do the work each toolchain release that includes a new LLVM version)